Shower Tray Waste and Trap: Position, Flow Rate and Grille

The waste is the part of a shower tray nobody gives a thought to until water starts pooling around your feet, or that faint drains smell turns up in the mornings. And it turns out this is exactly where you decide whether the shower works well for years. Here’s what really matters: where the waste goes, how much water it has to swallow, what to do about trap height, and how to keep the grille clean.

Where the waste goes: centred or to one end

There’s no universal “right” position. Where the shower tray waste sits comes down to one very specific detail in your bathroom: where the floor outlet is. That outlet is already set by the building work or the old installation, and the sensible thing is to fit the tray to it, not the other way round.

The two most common options:

• Centred waste. It looks balanced and spreads the falls evenly towards the gully. It works very well on square or near-square trays.
• End or side waste. This is the usual choice when the floor outlet sits against a wall or in a corner. On long trays (think 70×140 or 80×180) it’s often the most comfortable, since it leaves the whole standing area clear.

Because Aquatit trays are made to measure in mineral-filled resin, you choose the waste position when you order. You tell us where your outlet is and we drill the gully right there, with the fall already calculated towards that point. If you’re unsure about the dimensions, the 70×140 sizes page shows a format in high demand precisely because it allows an end waste.

Flow rate: making sure it swallows everything

This is the point that causes the most trouble and is the least understood. A pretty grille is no use if the trap underneath drains slowly. A rain head or a thermostatic mixer wide open can put out a fair bit of water, and if the waste doesn’t take it away at the same pace, a film of water builds up and rises over your feet.

A good shower tray trap should drain at around 30 to 40 litres a minute. Below that figure you start getting pooling with high-flow showers.

A waste draining 35 l/min versus one at 20 l/min looks the same on fitting day. You notice it every morning, when one clears the tray in seconds and the other leaves a puddle hanging around.

The real flow rate depends on the trap itself, but also on the installation: a waste pipe with too little fall or one bend too many takes a heavy toll. If you’re renovating, it’s worth checking that the floor waste has the right drop before you set the tray down.

Trap height and the problem with flush installs

Here’s the second big headache. The trap takes up height below the tray, and there isn’t always room. In renovations where the tray sits almost level with the finished floor, or on a slab with barely any clearance, a standard trap simply won’t fit.

For those cases there are extra-flat traps, much shallower. They come with a catch: in reducing height, many models also reduce the water seal and the flow rate. So it pays to choose carefully rather than settle for “it fits”. The ideal is an extra-flat trap that still drains with room to spare and keeps a good water seal against odours.

The simple advice: before you buy, measure the actual clearance under the tray. With that figure we can steer you on whether you need a standard or an extra-flat trap, whether in a Smooth finish or the anti-slip relief of the Slate range.

The grille: included, stainless steel and easy to clean

The grille is the visible piece, the one that catches hair and bits before they reach the trap. At Aquatit the grille comes in stainless steel and is included with the tray, just like the trap. No buying it separately, no hunting for odd sizes.

Keeping it clean couldn’t be simpler:

• Lift the grille off (it usually just rests in place or twists a quarter turn).
• Clear hair and built-up soap from the gully basket once a week.
• Rinse the grille and, if you like, wipe it with a mild descaler so the steel keeps its shine.

Five minutes a week heads off 90% of slow blockages.

Bad smells: it all comes down to the water seal

If your shower smells of drains, it’s nearly always down to a water seal that’s too weak or has dried out. The trap works by always holding back a little water that acts as a plug against the gases in the system. If that plug dries up (say, in a second home left shut for weeks) or the trap is too shallow to hold much water, the smells come up.

The fix is a trap with a decent water seal and, for showers used now and then, running the water for a moment every so often to top up the seal. That’s why we keep banging on about not choosing the extra-flat one on height alone.

What to specify on your order

The shower tray waste comes down to four decisions: position to suit your floor outlet, enough flow (aim for 30 to 40 l/min), a trap height that matches your clearance, and a grille you keep clean. At Aquatit the stainless steel trap and grille are included free on every tray, and you specify the waste position when you order, so the tray arrives ready for your install.

Want your tray with the waste exactly where you need it? Set it up on made-to-measure and get the price straight away, or tell us about your case via contact and we’ll help you get the trap right.