WEDNESDAY, JUNE 15, 2022 AT 4 PM – 7 PM

Farmers Market at Pinecrest

Pinecrest
Join Pinecrest on Wednesdays this summer for our Farmers Markets! Live music and several amazing vendors will join us on 3rd Street, beside Saucy Brew Works, and the sidewalk beside West Elm every Wednesday from 4-7 PM

This is the exterior of a townhome I was asked to inspect. During the inspection, I ran into a neighbor who told me that the roof of another garage, identical to the one pictured above two buildings down, had collapsed the previous winter under a snow load.

So, I decided to keep my eyes wide open as I went through the garage.

Above: trusses and truss connections

Some defects you have to search for, and some are pretty obvious. These first two defects were obvious from the doorway:

  • improper alterations; and
  • improper bearing points.

Trusses cannot be altered in any way without the approval of a structural engineer. When you see plywood gussets added at truss connections like these triangular gussets, then an alteration of some sort has obviously been made and you have to recommend evaluation by a structural engineer. So, that condition went into the report.

Trusses are designed to bear loads at very specific points. Typical roof trusses should not touch any interior walls and should bear only on the exterior walls. The two trusses at the left of the above photo are bearing on an offset portion of the garage wall.

A portion of the structural roof load was being transferred to the bottom chords of the trusses at a point at which they were not designed to support a load.

Above: the connection

Then I walked over and looked more closely at the connections where the trusses attached to the wall and found these problems:

  • inadequate metal connector (hanger);
  • inadequate fasteners (deck screws); and
  • improper fastener installation (through drywall).

These trusses would have best been supported by bearing directly on wall framing. The next best solution would be an engineer-designed ledger or engineer-specified hardware. And that may have been how they were originally built, but by the time I inspected them, 24-foot roof trusses were supported by joist hangers designed to support 2×4 joists. The hangers were fastened with four gold deck screws each.

Gold deck screws are designed to resist withdrawal. Fasteners for metal connectors such as joist hangers are designed to resist shear.

Withdrawal force is like the force which would be generated if you grabbed the head of a fastener with pliers and tried to pull it straight out.

Shear force is what’s used if you take a pair of heavy-duty wire cutters and cut the fastener. Fasteners designed to resist withdrawal, such as deck screws, are weak in shear resistance.

So, there were drastically undersized metal connectors fastened by badly under-strength fasteners.

To make matters worse, the screws were fastened through drywall, which doesn’t support the shaft of the screw and degrades the connection even further.

Above: gangnail integrity destroyed

And, once I looked really closely, I found more truss alterations. The gangnail had been pried loose and the spikes which form the actual mechanical connection were destroyed. In their place were a couple of bent-over nails. This condition represented a terrific loss of strength and this roof, too, was a candidate for catastrophic structural failure.

In summary, look carefully at connections for problems which may lead to structural issues, as some are more urgent than others. Be sure to call these out in your report. Also, all electrical receptacles in garages must be GFCI-protected, without exception.

Thermal insulation helps shield a building’s interior so that it’s less affected by the exterior temperature, thereby substantially reducing the building’s energy usage, as well as energy costs. This can provide commercial building owners with the greatest return on an initial investment of almost any building material, especially if the building relies on heating and/or air-conditioning.

The U.S. Department of Energy (DOE) found in 2012 that 34% of the energy costs for the average commercial building are spent on space heating and cooling. Energy efficiency has increasingly become a concern of both builders and owners of commercial buildings. In order to maximize efficiency, each component of the roofing system is examined closely and then rated in terms of its level of thermal resistance. In fact, the DOE also found that there was a 26% decrease in energy usage for space heating and cooling between 2003 and 2012. This supports the improvements made in roof systems and insulation overall.

Energy costs for the average commercial building are spent on space heating and cooling was 34% in 2012.

Adequate thermal insulation in a roofing system also reduces radiative losses that chill occupants in cold weather, and reduces interior surface temperatures in the summer, thereby optimizing the comfort of building occupants.

Consider the following scenario: On a hot summer day, the meeting room in an office building has an air temperature of 72º F, yet the room’s occupants are feeling uncomfortably warm. Further investigation reveals that the wall and ceiling surface temperatures are nearly 90º F. This scenario illustrates that people sense heat loss and gain such that the radiative warming of their bodies is relative to the walls and ceiling, and not the air temperature.

Additional benefits of thermal insulation include:

  • prevents the formation of condensation on exposed interior building surfaces;
  • relieves concentrated areas of stress in the membrane by distributing it over more extensive areas;
  • stabilizes the temperature of deck components through the reduction of temperature variations;
  • provides a flat surface as a substrate for membrane installation over steel decks;
  • in some instances, provides a fire-resistant barrier; and
  • availability in tapered designs to create positive drainage in areas where the roof deck is level.

Conventional Roof System

In a conventional roof system, insulation is installed under the roof membrane. This is the most common low-slope roof application.

The location of the insulation in a conventional roof system poses a few disadvantages. When inspecting, look signs of the following:

  1. Membrane aging. When insulation is used directly under the roof membrane, solar heat does not readily pass through the roofing system, which increases the roof’s surface temperature. This, in turn, accelerates the oxidation and evaporation of volatile oils in bitumen-based membranes. Look for brittle, cracked, or alligatoring surfaces. This is also caused by ultraviolet degradation.
  2. Thermally induced expansion and contraction. The roof membrane may experience increased expansion and contraction from the increased surface temperature and rapid daily temperature changes. Rapid daily temperatures are caused by the lack of heat transfer through the roof assembly.During a hot day, the roof membrane directly next to the insulation becomes much hotter than the exposed surface and air temperature. Then, in the evening, when the sun goes down, the entire membrane’s temperature returns to air temperature rather than the interior temperature. This can also cause membrane aging, along with ridging, splitting, and lap-shear stress. Long-term thermally induced expansion and contraction can also cause the insulation to shift. Look for changes in the membrane surface.
  3. Moisture within the roofing system. The interior and exterior surface temperature range caused by thermal insulation may increase the likelihood of water vapor entering through the warm side and condensing within the roof system. Moisture entrapment can be detrimental, as it can destroy thermal insulation, enter cracks and joints of the roof deck, leak into the building’s ceiling, and even cause the membrane to separate due to freezing and thawing cycles. Look for sagging in the roof surface, efflorescence, and corrosion of accessories (like fasteners). Moisture may enter the roof system during the installation phase or while in service. Ventilation and vapor barriers help to mitigate these effects.

Mechanical fasteners are exposed due to membrane shrinkage.

Ponding has formed due to insulation collapse.

Protected Membrane Roof (PMR)

In a protected membrane roof, also known as an inverted roof membrane assembly (IRMA), the insulation is installed on top of the membrane. The insulation may be exposed to water, so it should have minimal water absorption characteristics. Extruded polystyrene (XPS) is the most suitable type. The XPS boards are placed over the membrane and held down by a layer of ballast or lose pavers on top.

If a ballast is used, a filter fabric should be placed between the ballast insulation to prevent damage to the XPS. The other disadvantages of insulation discussed for the conventional roof system do not apply, since the roof membrane isn’t exposed. However, if the ballast or lose pavers on the exposed surface shift, the roofing system may be compromised; this is common after high winds.

Ideal Characteristics of Thermal Insulation for Low-Slope Roofs:

  • Strength: Able to resist damage from compression due to assembly, as well as roof traffic.
  • Dimensional stability: Limited expansion and contraction from temperature and moisture fluctuations.
  • Attachment: Surfaces provide for secure attachment.
  • Stable thermal resistance: Little to no degradation with environmental changes and age.
  • Thermal resistance: Low thermal conductivity so that the greatest thermal resistance can be achieved with the least amount of material.
  • Moisture resistance: Resists the damage of water and moisture vapor.
  • Fire resistance: Non-combustible.
  • Impact resistance: Great enough strength, density, and rigidity to resist damage due to impact during both installation and use.
  • Compatibility of components: Well-matched with the other components of the roof assembly.
  • Chemical compatibility: Able to withstand the effects of being in contact with bitumen, adhesives, solvents, and application temperatures.

No type of thermal insulation will be faultless in all of these areas. Also note that there are many types of thermal insulation, and each type has specific installation and compatibility requirements as determined by its manufacturer. The advantages and disadvantages of insulation discussed here are general and not all-inclusive. Read Types of Low-Slope Roof Insulation for more in-depth information related to specific types of insulation, or check with individual manufacturers.

The Takeaway for Commercial Property Inspectors

A large percentage of energy costs for the average commercial building is spent on heating and cooling. Thermal insulation helps reduce energy usage and energy costs while working to maintain the desired comfort level for building occupants. However, thermal insulation does have some disadvantages that are correlated to the location of the insulation.
The inspector should identify whether the roofing assembly is a conventional roof system or a protected membrane system (PMR). In a conventional roof system, the membrane is visible or has dime-sized aggregate embedded into the membrane. Although it is the most common type, it’s more prone to in-service defects than protected membrane systems. Some of the more obvious defects correspond to the location of the insulation under the membrane.

In a protected membrane system, the membrane can’t be seen because it’s covered in a layer of gravel or lose pavers. As the membrane is located under the insulation, it is less prone to mechanical and weather-related defects if it’s well-designed, installed, and maintained.

AEC Inspection Services
www.aecinspectionservices.com
inspect@aecinspectionservices.com
4941 SW 74th Ct
Miami Florida 33155

Save money and energy at home! Learn ways to save energy.

Most people don’t know how easy it is to make their homes run on less energy, and here at InterNACHI, we want to change that.

Drastic reductions in heating, cooling and electricity costs can be accomplished through very simple changes, most of which homeowners can do themselves. Of course, for homeowners who want to take advantage of the most up-to-date knowledge and systems in home energy efficiency, InterNACHI energy auditors can perform in-depth testing to find the best energy solutions for your particular home.

Why make your home more energy efficient? Here are a few good reasons:

  • Federal, state, utility and local jurisdictions’ financial incentives, such as tax breaks, are very advantageous for homeowners in most parts of the U.S.
  • It saves money. It costs less to power a home that has been converted to be more energy-efficient.
  • It increases the comfort level indoors.
  • It reduces our impact on climate change. Many scientists now believe that excessive energy consumption contributes significantly to global warming.
  • It reduces pollution. Conventional power production introduces pollutants that find their way into the air, soil and water supplies.

1. Find better ways to heat and cool your house.

As much as half of the energy used in homes goes toward heating and cooling. The following are a few ways that energy bills can be reduced through adjustments to the heating and cooling systems:

  • Install a ceiling fan. Ceiling fans can be used in place of air conditioners, which require a large amount of energy.
  • Periodically replace air filters in air conditioners and heaters.
  • Set thermostats to an appropriate temperature. Specifically, they should be turned down at night and when no one is home. In most homes, about 2% of the heating bill will be saved for each degree that the thermostat is lowered for at least eight hours each day. Turning down the thermostat from 75° F to 70° F, for example, saves about 10% on heating costs.
  • Install a programmable thermostat. A programmable thermostat saves money by allowing heating and cooling appliances to be automatically turned down during times that no one is home and at night. Programmable thermostats contain no mercury and, in some climate zones, can save up to $150 per year in energy costs.
  • Install a wood stove or a pellet stove. These are more efficient sources of heat than furnaces.
  • At night, curtains drawn over windows will better insulate the room.

Image of a high-efficiency thermostat at the InterNACHI® House of Horrors® in Colorado.

2. Install a tankless water heater.

Demand-type water heaters (tankless or instantaneous) provide hot water only as it is needed. They don’t produce the standby energy losses associated with traditional storage water heaters, which will save on energy costs. Tankless water heaters heat water directly without the use of a storage tank. When a hot water tap is turned on, cold water travels through a pipe into the unit. A gas burner or an electric element heats the water. As a result, demand water heaters deliver a constant supply of hot water. You don’t need to wait for a storage tank to fill up with enough hot water.

3. Replace incandescent lights.

The average household dedicates 11% of its energy budget to lighting. Traditional incandescent lights convert approximately only 10% of the energy they consume into light, while the rest becomes heat. The use of new lighting technologies, such as light-emitting diodes (LEDs) and compact fluorescent lamps (CFLs), can reduce the energy use required by lighting by 50% to 75%. Advances in lighting controls offer further energy savings by reducing the amount of time that lights are on but not being used. Here are some facts about CFLs and LEDs:

  • CFLs use 75% less energy and last about 10 times longer than traditional incandescent bulbs.
  • LEDs last even longer than CFLs and consume less energy.
  • LEDs have no moving parts and, unlike CFLs, they contain no mercury.

4. Seal and insulate your home.

Sealing and insulating your home is one of the most cost-effective ways to make a home more comfortable and energy-efficient, and you can do it yourself. A tightly sealed home can improve comfort and indoor air quality while reducing utility bills. An InterNACHI energy auditor can assess leakage in the building envelope and recommend fixes that will dramatically increase comfort and energy savings.

The following are some common places where leakage may occur:

  • electrical receptacles/outlets;
  • mail slots;
  • around pipes and wires;
  • wall- or window-mounted air conditioners;
  • attic hatches;
  • fireplace dampers;
  • inadequate weatherstripping around doors;
  • baseboards;
  • window frames; and
  • switch plates.

Because hot air rises, air leaks are most likely to occur in the attic. Homeowners can perform a variety of repairs and maintenance to their attics that save them money on cooling and heating, such as:

  • Plug the large holes. Locations in the attic where the leakage is most likely to be the greatest are where walls meet the attic floor, behind and under attic knee walls, and in dropped-ceiling areas.
  • Seal the small holes. You can easily do this by looking for areas where the insulation is darkened. Darkened insulation is a result of dusty interior air being filtered by insulation before leaking through small holes in the building envelope. In cold weather, you may see frosty areas in the insulation caused by warm, moist air condensing and then freezing as it hits the cold attic air. In warmer weather, you’ll find water staining in these same areas. Use expanding foam or caulk to seal the openings around plumbing vent pipes and electrical wires. Cover the areas with insulation after the caulk is dry.
  • Seal up the attic access panel with weatherstripping. You can cut a piece of fiberglass or rigid foamboard insulation in the same size as the attic hatch and glue it to the back of the attic access panel. If you have pull-down attic stairs or an attic door, these should be sealed in a similar manner.

5. Install efficient showerheads and toilets.

The following systems can be installed to conserve water usage in homes:

  • low-flow showerheads. They are available in different flow rates, and some have a pause button that shuts off the water while the bather lathers up;
  • low-flow toilets. Toilets consume 30% to 40% of the total water used in homes, making them the biggest water users. Replacing an older 3.5-gallon toilet with a modern, low-flow 1.6-gallon toilet can reduce usage an average of 2 gallons per flush (GPF), saving 12,000 gallons of water per year. Low-flow toilets usually have “1.6 GPF” marked on the bowl behind the seat or inside the tank;
  • vacuum-assist toilets. This type of toilet has a vacuum chamber that uses a siphon action to suck air from the trap beneath the bowl, allowing it to quickly fill with water to clear waste. Vacuum-assist toilets are relatively quiet; and
  • dual-flush toilets. Dual-flush toilets have been used in Europe and Australia for years and are now gaining in popularity in the U.S. Dual-flush toilets let you choose between a 1-gallon (or less) flush for liquid waste and a 1.6-gallon flush for solid waste. Dual-flush 1.6-GPF toilets reduce water consumption by an additional 30%.

6. Use appliances and electronics responsibly.

Appliances and electronics account for about 20% of household energy bills in a typical U.S. home. The following are tips that will reduce the required energy of electronics and appliances:

  • Refrigerators and freezers should not be located near the stove, dishwasher or heat vents, or exposed to direct sunlight. Exposure to warm areas will force them to use more energy to remain cool.
  • Computers should be shut off when not in use. If unattended computers must be left on, their monitors should be shut off. According to some studies, computers account for approximately 3% of all energy consumption in the United States.
  • Use efficient ENERGY STAR-rated appliances and electronics. These devices, approved by the U.S. Department of Energy and the Environmental Protection Agency’s ENERGY STAR Program, include TVs, home theater systems, DVD players, CD players, receivers, speakers, and more. According to the EPA, if just 10% of homes used energy-efficient appliances, it would reduce carbon emissions by the equivalent of 1.7 million acres of trees.
  • Chargers, such as those used for laptops and cell phones, consume energy when they are plugged in. When they are not connected to electronics, chargers should be unplugged.
  • Laptop computers consume considerably less electricity than desktop computers.

7. Install daylighting as an alternative to electrical lighting.

Daylighting is the practice of using natural light to illuminate the home’s interior. It can be achieved using the following approaches:

  • skylights. It’s important that they be double-pane or they may not be cost-effective. Flashing skylights correctly is key to avoiding leaks;
  • light shelves. Light shelves are passive devices designed to bounce light deep into a building. They may be interior or exterior. Light shelves can introduce light into a space up to 2½ times the distance from the floor to the top of the window, and advanced light shelves may introduce four times that amount;
  • clerestory windows. Clerestory windows are short, wide windows set high on the wall. Protected from the summer sun by the roof overhang, they allow winter sun to shine through for natural lighting and warmth; and
  • light tubes. Light tubes use a special lens designed to amplify low-level light and reduce light intensity from the midday sun. Sunlight is channeled through a tube coated with highly reflective material and then enters the living space through a diffuser designed to distribute light evenly.

8. Insulate windows and doors.

About one-third of the home’s total heat loss usually occurs through windows and doors. The following are ways to reduce energy lost through windows and doors:

  • Seal all window edges and cracks with rope caulk. This is the cheapest and simplest option.
  • Windows can be weatherstripped with a special lining that is inserted between the window and the frame. For doors, apply weatherstripping around the whole perimeter to ensure a tight seal when they’re closed. Install quality door sweeps on the bottom of the doors if they aren’t already in place.
  • Install storm windows at windows with only single panes. A removable glass frame can be installed over an existing window.
  • If existing windows have rotted or damaged wood, cracked glass, missing putty, poorly fitting sashes, or locks that don’t work, they should be repaired or replaced.

9. Cook smart.

An enormous amount of energy is wasted while cooking. The following recommendations and statistics illustrate less wasteful ways of cooking:

  • Convection ovens are more efficient that conventional ovens. They use fans to force hot air to circulate more evenly, thereby allowing food to be cooked at a lower temperature. Convection ovens use approximately 20% less electricity than conventional ovens.
  • Microwave ovens consume approximately 80% less energy than conventional ovens.
  • Pans should be placed on the matching size heating element or flame.
  • Using lids on pots and pans will heat food more quickly than cooking in uncovered pots and pans.
  • Pressure cookers reduce cooking time dramatically.
  • When using conventional ovens, food should be placed on the top rack. The top rack is hotter and will cook food faster.

10. Change the way you do laundry.

  • Do not use the medium setting on your washer. Wait until you have a full load of clothes, as the medium setting saves less than half of the water and energy used for a full load.
  • Avoid using high-temperature settings when clothes are not very soiled. Water that is 140° F uses far more energy than 103° F for the warm-water setting, but 140° F isn’t that much more effective for getting clothes clean.
  • Clean the lint trap every time before you use the dryer. Not only is excess lint a fire hazard, but it will prolong the amount of time required for your clothes to dry.
  • If possible, air-dry your clothes on lines and racks.
  • Spin-dry or wring clothes out before putting them into a dryer.

Homeowners who take the initiative to make these changes usually discover that the energy savings are more than worth the effort. InterNACHI home inspectors can make this process much easier because they can perform a more comprehensive assessment of energy-savings potential than the average homeowner can.

Nelson Salazar
AEC Inspection Services, LLC
d/b/a AEC Inspection Services
inspec@aecinspectionservices.com
4941 South West 74th Court
Miami Florida 33155

The following items are essential tools, but this list is by no means exhaustive. Feel free to ask an AEC inspector during your next inspection about other tools that you might find useful.

1. Plunger

A clogged sink or toilet is one of the most inconvenient household problems that you will face. With a plunger on hand, however, you can usually remedy these plumbing issues relatively quickly. It is best to have two plungers — one for the sink and one for the toilet.

2. Combination Wrench Set

One end of a combination wrench set is open and the other end is a closed loop. Nuts and bolts are manufactured in standard and metric sizes, and because both varieties are widely used, you’ll need both sets of wrenches. For the most control and leverage, always pull the wrench toward you, instead of pushing on it. Also, avoid over-tightening.3. Slip-Joint Pliers

Use slip-joint pliers to grab hold of a nail, a nut, a bolt, and much more. These types of pliers are versatile because of the jaws, which feature both flat and curved areas for gripping many types of objects. There is also a built-in slip-joint, which allows the user to quickly adjust the jaw size to suit most tasks.

4. Adjustable Wrench

Adjustable wrenches are somewhat awkward to use and can damage a bolt or nut if they are not handled properly. However, adjustable wrenches are ideal for situations where you need two wrenches of the same size. Screw the jaws all the way closed to avoid damaging the bolt or nut.

5. Caulking Gun

Caulking is the process of sealing up cracks and gaps in various structures and certain types of piping. Caulking can provide noise mitigation and thermal insulation, and control water penetration. Caulk should be applied only to areas that are clean and dry.

6. Flashlight

None of the tools in this list is of any use if you cannot visually inspect the situation. The problem, and solution, are apparent only with a good flashlight. A traditional two-battery flashlight is usually sufficient, as larger flashlights may be too unwieldy.

7. Tape Measure

Measuring house projects requires a tape measure — not a ruler or a yardstick. Tape measures come in many lengths, although 25 feet is best. Measure everything at least twice to ensure accuracy.

8. Hacksaw

A hacksaw is useful for cutting metal objects, such as pipes, bolts and brackets. Hacksaws look thin and flimsy, but they’ll easily cut through even the hardest of metals. Blades are replaceable, so focus your purchase on a quality hacksaw frame.

9. Torpedo Level

Only a level can be used to determine if something, such as a shelf, appliance or picture, is correctly oriented. The torpedo-style level is unique because it not only shows when an object is perfectly horizontal or vertical, but it also has a gauge that shows when an object is at a 45-degree angle. The bubble in the viewfinder must be exactly in the middle — not merely close.

10. Safety Glasses / Goggles

For all tasks involving a hammer or a power tool, you should always wear safety glasses or goggles. They should also be worn while you mix chemicals.

11. Claw Hammer

A good hammer is one of the most important tools you can own. Use it to drive and remove nails, to pry wood loose from the house, and in combination with other tools. They come in a variety of sizes, although a 16-ounce hammer is the best all-purpose choice.

12. Screwdriver Set

It is best to have four screwdrivers: a small and large version of both a flathead and a Phillips-head screwdriver. Electrical screwdrivers are sometimes convenient, but they’re no substitute. Manual screwdrivers can reach into more places and they are less likely to damage the screw.

13. Wire Cutters

Wire cutters are pliers designed to cut wires and small nails. The side-cutting style (unlike the stronger end-cutting style) is handy, but not strong enough to cut small nails.

14. Respirator / Safety Mask

While paints and other coatings are now manufactured to be less toxic (and lead-free) than in previous decades, most still contain dangerous chemicals, which is why you should wear a mask to avoid accidentally inhaling. A mask should also be worn when working in dusty and dirty environments. Disposable masks usually come in packs of 10 and should be thrown away after use. Full and half-face respirators can be used to prevent the inhalation of very fine particles that ordinary facemasks will not stop.

15. Duct Tape

This tape is extremely strong and adaptable. Originally, it was widely used to make temporary repairs to many types of military equipment. Today, it’s one of the key items specified for home emergency kits because it is water-resistant and extremely sticky.

by Nelson Salazar, CPI® and AEC Inspections Services

Backflow is the reversal of the normal and intended direction of water flow in a water system. Devices and assemblies known as backflow preventers are installed to prevent backflow, which can contaminate potable water supplies.

Why is backflow a problem?

Backflow is a potential problem in a water system because it can spread contaminated water back through a distribution system. For example, backflow at uncontrolled cross connections (cross-connections are any actual or potential connection between the public water supply and a source of contamination or pollution) can allow pollutants or contaminants to enter the potable water system. Sickness can result from ingesting water that has been contaminated due to backflow.

Backflow may occur under the following two conditions:

  • back-pressure:
    Back-pressure is the reverse from normal flow direction within a piping system as the result of the downstream pressure being higher than the supply pressure. This reduction in supply pressure occurs whenever the amount of water being used exceeds the amount of water being supplied (such as during water-line flushing, fire-fighting, or breaks in water mains).
  • back-siphonage:
    Back-siphonage is the reverse from normal flow direction within a piping system that is caused by negative pressure in the supply piping (i.e., the reversal of normal flow in a system caused by a vacuum or partial vacuum within the water supply piping). Back-siphonage can occur when there is a high velocity in a pipe line, when there is a line repair or break that is lower than a service point, or when there is lowered main pressure due to high-water withdrawal rate (such as during fire-fighting or water-main flushing).

Atmospheric Vacuum Breakers

Backflow prevention for residences is most commonly accomplished through the use of atmospheric vacuum breakers (AVBs). AVBs operate by allowing the entry of air into a pipe so that a siphon cannot form. AVBs are bent at 90 degrees and are usually composed of brass. Compared with backflow preventer assembles, AVBs are small, simple and inexpensive devices that require little maintenance or testing. They have long life spans and are suitable for residential purposes such as sprinkler systems. InterNACHI inspectors can check for the following:

  • The AVB must be at least 6 inches above any higher point downstream of the device. For this reason, they can never be installed below grade. Even if they are installed 6 inches above grade, inspectors should make sure that they are not installed less than 6 inches above some other point in the system downstream of the device.
  • The AVB cannot be installed in an enclosure containing air contaminants. If contaminated air enters the water piping, it can poison the potable water supply.
  • A shut-off valve should never be placed downstream of any AVB, as this would result in continuous pressure on the AVB.
  • AVBs cannot be subject to continuous pressure for 12 hours in any 24-hour period or they may malfunction.
  • Spillage of water from the top of the AVB is an indication that the device has failed and needs to be replaced.

Types of Backflow Preventer Assemblies

Some types of assemblies are common in commercial and agricultural applications but are rare for residential uses. The appropriate type of backflow preventer for any given application will depend on the degree of potential hazard. The primary types of backflow preventers appropriate for use at municipalities and utilities are:

  • double check valves: These are commonly used in elevated tanks and non-toxic boilers. Double check-valve assemblies are effective against backflow caused by back-pressure and back-siphonage and are used to protect the potable water system from low-hazard substances. Double-checks consist of two positive-seating check valves installed as a unit between two tightly closing shut-off valves, and are fitted with testcocks.
  • reduced pressure principle assemblies: These are commonly used in industrial plants, hospitals, morgues, chemical plants, irrigation systems, boilers, and fire sprinkler systems. Reduced pressure principle assemblies (RPs) protect against back-pressure and back-siphonage of pollutants and contaminants. The assembly is comprised of two internally loaded, independently operating check valves with a mechanically independent, hydraulically dependent relief valve between them.
  • pressure vacuum breakers: These are commonly used in industrial plants, cooling towers, laboratories, laundries, swimming pools, lawn sprinkler systems, and fire sprinkler systems. Pressure vacuum breakers use a check valve designed to close with the aid of a spring when water flow stops. Its air-inlet valve opens when the internal pressure is one psi above atmospheric pressure, preventing non-potable water from being siphoned back into the potable system. The assembly includes resilient, seated shut-off valves and testcocks.

Requirements for Testers and Inspectors

A number of organizations, such as the American Water Works Association (AWWA) and the American Backflow Prevention Association (ABPA) offer certification courses designed to train professionals to test backflow preventers. Requirements for training vary by jurisdiction. Inspection of backflow preventers requires knowledge of installation requirements, although inspectors are not required to become certified.

In summary, backflow preventers are designed to prevent the reverse flow of water in a potable water system. They come in a number of different types, each of which is suited for different purposes.

Contact us at inspect@aecinspectionsservices.com
Nelson Salazar, CPI® and AEC Inspections Services
4941 South West 74th Court, Miami Florida 33155