A floor waste gully keeps drain air out with a few centimetres of water sitting in its trap. That works while the floor gets wet regularly. In a spare ensuite, a plant room, a laundry that's rarely flooded, a sauna or a steam room, the water evaporates, the seal goes, and the room starts smelling of drain. There are three different products for this problem, and they solve it in different ways.
The three options at a glance
| Trap primer valve | Press-fit trap seal | Floor waste plug | |
|---|---|---|---|
| Product | Watts LFTP3T-AUS | RectorSeal Drain Smell Stop | Allproof TFW80PLUG |
| How it works | Feeds a small charge of water into the trap whenever its cold water line is used | Rubber membrane and air relief valve close behind draining water, so no water seal is needed | Solid cover over the waste opening while closed |
| Sizes | 15mm cold water inlet | 50mm, 80mm, 100mm drains | 80mm, Allproof Leak Control Flange only |
| Price | $159.50 | $24.99 / $26.99 / $39.99 | $190.27 round, $195.21 square |
| Install | Plumbed into a cold line and piped to the trap | Push-fit into the drain opening, no tools | Sits in the flange in place of the grate |
Trap primer valve: keep the water seal working
The Watts LFTP3T-AUS is pressure-activated. Each time the cold water line it's teed off is used, it sends a small charge of water to the floor waste trap, so the normal water seal never dries out. It needs no power or batteries, has vacuum breaker ports, comes with a service ball valve, and is lead free brass.
Its one dependency is obvious but easy to miss: it only primes when that cold line is actually used. Tee it off a fixture that sees daily use, such as a basin or WC in the same area. Put it on a line that's as idle as the floor waste, and you've moved the problem rather than fixed it. It's the option that keeps the drainage working exactly as designed, which makes it the natural choice in commercial and new-build work where the floor waste has to stay a functioning floor waste.
Press-fit trap seal: no water to evaporate
RectorSeal's Drain Smell Stop takes the opposite approach. It push-fits into the drain opening, and a flexible rubber membrane with an air relief valve lets water drain through, then closes behind it. With no standing water there's nothing to evaporate. RectorSeal describes it as a permanent fix with nothing to maintain, and backs it with a minimum 3 year limited warranty. Those are the manufacturer's claims.
It's the cheapest option by a wide margin and the quickest to fit, which makes it the obvious retrofit for a spare-bathroom shower or laundry floor waste that's started smelling. Two things to check first. The listing doesn't show a WaterMark licence, and a device fitted into a floor waste is something your certifier or plumbing regulator may want to see accepted, so confirm before using it on a job you're certifying. Also, the 100mm size is currently out of stock, with stock expected mid-November. The 50mm and 80mm sizes are available.
Floor waste plug: close the opening
Allproof's cast chrome-on-brass Tile Floor Waste Plug doesn't touch the trap at all. It sits in an 80mm Allproof Leak Control Flange in place of the grate and covers the opening while it's closed. It's the most expensive of the three and only fits that one flange, so it's usually specified from the start rather than retrofitted. Its natural home is steam rooms and saunas, where the floor waste sits closed between wash-downs and a solid chrome finish suits the room. We cover that in detail in Floor Waste Plugs for Steam Rooms and Saunas.
A plug only works while it's closed, and the trap behind it can still dry out. It also stops the waste doing its job while it's shut, so don't use it on a floor waste that's there to catch overflow.
Which one to use
- New build or commercial, floor waste must stay functional: trap primer off a regularly used cold line.
- Existing floor waste that's started smelling, quick fix: press-fit trap seal, once you've confirmed it's acceptable for that job.
- Steam room or sauna on an Allproof 80mm flange: floor waste plug, opened for wash-down.
Whichever you choose, how a floor waste trap is kept charged is set by AS/NZS 3500.2 and your local plumbing regulator. Charging the gully from a nearby fixture's waste remains the conventional approach. Check with the certifier before relying on a device instead.
Frequently Asked Questions
Why does my floor waste smell when the room isn't used?
Usually because the water in the floor waste trap has evaporated. With no water seal, air from the drainage system can come up through the grate. Pouring water down the waste restores the seal for a while; a trap primer, press-fit seal or plug deals with it longer term.
Does a trap primer need power?
No. The Watts LFTP3T-AUS is pressure-activated and primes the trap whenever the 15mm cold water line it's connected to is used.
Is a press-fit trap seal allowed in Australia?
Check before using it on a certified job. The RectorSeal Drain Smell Stop listing doesn't show a WaterMark licence, and your certifier or plumbing regulator decides whether a device can be used to keep a floor waste trap sealed.
Will the Allproof floor waste plug stop the trap drying out?
No. It covers the opening while closed, but the trap behind it can still lose its water. It suits steam rooms and saunas where the waste stays closed between wash-downs.