Specifying waterless trap primers to minimize evaporation and conserve water

drains_220By Rick Ensley

Water-efficient toilets, faucets and other plumbing fixtures have become routine specifications in the last decade. However, the next plateau of water conservation for plumbing engineers will be waterless, or floor drain, trap primers.

California’s record-breaking drought brought the water conservation issue to the forefront, especially after Governor Jerry Brown’s 25 percent water reduction mandate. As water shortages gradually become the new normal nationally, water-conserving plumbing products, such as waterless trap primers (sometimes referred to as a barrier-type trap seal protection devices in plumbing codes), will become significant factors in solving water conservation challenges, because they provide 100 percent water-saving efficiency over traditional methods. Building owners will look to plumbing engineers for these types of water-conserving solutions in new construction projects. Meanwhile, maintenance departments and plumbing service contractors will be relied on in facility retrofits.

Since coming on the market as an alternative to potable or fresh water-supplied trap primers, the waterless trap primer’s lure was its ability to prevent floor drain sewer gas ingress into the breathing spaces by minimizing trap evaporation. Most waterless trap primers feature a one-way membrane that acts similar to a check valve. It’s the membrane’s tight-seal that prevents sewer gas and insect ingress, while also minimizing evaporation of the trap seal. Thus, continual replenishment of the trap seal via water-supplied trap primers from the building water supply is not necessary. The membrane is sensitive enough to open from the weight of just 4 ounces of water draining from above in a shower stall or floor wash-down. But, it is strong enough to stay closed and sealed to minimize evaporation and eliminate sewer gas odor.

Today, an estimated 70 percent of new construction drain specifications still rely on old-school methods of a water-supplied trap primer or a drainage-supplied trap primer to prevent sewer gas ingress. Only an estimated 30 percent of projects are specified with waterless trap primers. But, that number is expected to grow exponentially as more geographical areas are subjected to droughts or government water restrictions.

A water-supplied trap primer typically uses 4-8 ounces of water at a time. Some models are adjustable. After adding evaporation and multiplying the number of drains in a commercial building, the water use can quickly turn from ounces to many gallons per hour.

Besides equipment, installation costs and water usage, maintenance is a significant disadvantage of water-supplied trap primers. Depending on the minerals inherent in a geographical area’s water supply, water-supplied trap primers can clog from calcification and other scaling processes. A dry, clogged, inoperable water-supplied trap primer obviously doesn’t provide any trap seal protection. Replacing a water-supplied trap primer many times requires breaking up the floor for access, which can cost upwards of $1,000 each in materials and mostly labor.

California State University, Chico

Maintenance and replacement costs are what drew Robert Francis, lead plumber at California State University, Chico, toward waterless trap primers. Francis used them as replacements to failed water-supplied trap primers, which resulted in significant savings for the university.

One instance of savings was a result of a change in a mechanical room located remotely from any fast-closing or flush valves. The location made the installed water-supplied trap primers malfunction and caused several floor sink traps to constantly dry out and allow sewer gas odor ingress, according to Francis. Fearing sewer gas could potentially infiltrate nearby fresh air intakes, Francis installed waterless trap primers. Francis said they took less than a minute to install, eliminated sewer gas ingress and allowed full drain functions. He also reported that the waterless trap primers could be easily removed if drain cleaning was required.


Not all building inspectors and their jurisdictions accept waterless trap primers, but many designs are ASSE-1072 tested and certified. ASSE-1072 is the national consensus standard for “Barrier Type Trap Seal Protection Devices.” ASSE-1072 has also been adopted into two of three national standard codes — the National Standard Plumbing Code (NSPC)-2012 and the International Plumbing Code (IPC)-2015. Both allow certified compliant devices when requiring a means of protecting the trap seal from evaporation.

Some waterless trap primer models are approved or accepted nationally for all retrofit uses. New construction use as a water-supplied trap primer substitute is currently state-by-state (see sidebar). Waterless floor drain traps are fully-approved in 15 states, widely-approved in 13 states and partially-approved in five states. A state that does not full-approve them might have a local jurisdiction approve them because they have adopted ASSE-1072.

A good strategy for engineers is to specify a water-supplied trap primer, when required, and add a waterless trap primer (approximately a $50 addition with less than five minutes of installation labor) to the specification as a back-up plan. Since the water-supplied version can potentially fail in as little as a year, waterless versions, which have warranties as long as 10 years and have proven records of remaining viable beyond their warranty, will provide the sewer gas protection. Then, it’s the building owner’s decision if and when to outlay hundreds of dollars for repairing or replacing the water-supplied version.

Choosing waterless trap primers

Generally, waterless trap primers fall under the auspices of “good, better and best.” Therefore, it’s the consulting engineer and/or contractor’s responsibility to specify a particular brand they deem as the best and most compliant.

There are also different degrees of ASSE-1072 certification, and it’s the contractor’s responsibility to investigate which devices are fully certified. For example, certification results will reveal some brands don’t meet the requirements to withstand the effects of dirt, debris, floor wax, and mop strands, or are restricted to certain flooring materials.

The future looks bright for waterless trap primers, especially in light of the fact that water conservation is becoming an increasingly important factor in plumbing specification and maintenance.

Rick Ensley is the SureSeal product manager at RectorSeal Corp., in Houston, Texas. RectorSeal is a leading manufacturer of plumbing and HVACR products that acquired the SureSeal brand in 2015. Ensley spent 10 years as a plumbing installer, four years in plumbing wholesale and three years with a plumbing manufacturer’s representative firm before joining SureSeal six years ago. SureSeal is a green, waterless, barrier-type trap seal protection device fully-certified under ASSE-1072 and accepted under The National Plumbing Code of Canada. To receive assistance with codes or inspections, please contact RectorSeal’s customer service at 800-231-3345, rensley@rectorseal.com, or www.rectorseal.com.