Knowing the Difference Between Trap Seals and Trap Primers

Could Save Project Capital and Maintenance Costs

By Rick Ensley

For decades the plumbing industry has depended on water-supplied trap primers for maintaining floor drain trap water levels, thus preventing potentially dangerous and always annoying indoor air quality (IAQ) issues caused by sewer gas infiltration into occupied spaces.

The most common trap primers are connected to a water line and activated via pressure fluctuation from a nearby urinal or water closet flush that maintains trap water levels. Other types divert gray water to the trap from nearby sink drains.

Trap primers’ main disadvantage is maintenance. Like many plumbing fixtures, their supply orifices are easily blocked by scale or corrosion. Cleaning or replacing them can be an expensive proposition, especially when they require floor and wall demolition/repair for access.

Comparatively, the recently-developed waterless barrier-type trap seal protection device circumvents these disadvantages because it’s virtually maintenance-free. Most floor drain trap seals are push-fit, with an EPDM or silicone-based fittings featuring a one-way membrane that acts similar to a check valve. The strong membrane’s tight-seal prevents sewer gas and insect ingress while also protecting against total trap water evaporation for months. Furthermore, the membrane is sensitive enough to open from the weight of just four ounces of water draining from a shower stall or floor wash-down.

Building codes are quickly changing across North America to allow trap seal use in lieu of trap primers. In many jurisdictions, trap seals are allowed as substitutes in retrofit situations where trap primers have failed. Opening and closing floors or walls to replace trap primers can many times cost upwards of $1,000 each, so a trap seal that installs in less than a minute after removing the floor drain grate can represent a significant savings.

New construction is a different story. Trap seals that carry an ASSE-1072 test and certification by a third party test lab may be substituted for trap primers in new construction, depending on the local jurisdiction and its inspectors. Plumbing consulting engineers that still want trap primers in their specifications might consider combining them with trap seals. When the trap primer’s lifecycle ends, the trap seal can still offer the facility sewer gas protection.

It’s the consulting engineer and/or contractor’s responsibility to specify a particular brand they deem as the best and compliant with ASSE-1072. It’s important to specify a brand since some brands don’t meet ASSE-1072’s requirements to withstand the effects of dirt, debris, floor wax and grease-laden waste. Typically the code-compliant models also have a built-in relief valve for eliminating potential air locks between the trap seal and the trap seal device that prevent floor water from draining properly.

There are also some new trap seal models with an added check valve benefit to protect against property-damaging water back-ups ranging up to five feet of head pressure.

Besides minimizing trap water evaporation reduction and maintenance, waterless trap seals are also considered green because they don’t require continual trap water filling, thus they complement water conservation efforts.

Some waterless trap seals are approved or accepted nationally for all retrofit uses. New construction specification depends on jurisdictions that have adopted ASSE-1072.

The following list presents approval levels by state and province:

  • Fully-Approved: Colorado, Connecticut, Illinois, Indiana, Kentucky, Louisiana, Massachusetts, Minnesota, North Carolina, New Jersey, New Mexico, Tennessee, Utah, Wisconsin and District of Columbia. Also Ontario and Quebec;
  • Widely-Approved: Alabama, Arkansas, Arizona, Georgia, Kansas, Missouri, Mississippi, Nevada, New York (except New York City), Pennsylvania, Rhode Island, Texas, and Washington;
  • Partially-Approved: Delaware, Oklahoma, South Carolina, and Virginia;

Some Approval and Currently Considering: Alaska, California, Florida, Hawaii, Iowa, Maine, Maryland, Montana, New England, North Dakota, Oregon, South Dakota, Vermont, West Virginia, Wyoming, Puerto Rico, and most of Canada outside of Ontario and Quebec