I am replacing an existing tray because of my and my wife's advancing years. The one we have is on legs and consequently is quite high off the ground and my wife in particular is nervous of slipping and falling when exiting the shower. So we have gone for a large (1400 x 900mm) low profile tray to replace it. There are other consequential benefits as we will be using decorative PVC panels to cover the existing tiles (no more mouldy grout lines) and having a single sheet of glass (like a walk-in shower) so no doors with easier access and again no mouldy crevices associated with sliding doors!

We are in a bungalow with a concrete floor so by definition we have to excavate a channel in the concrete in which to site the trap and pipework to connect to the 110mm main drain. This has all been done (see photo). My dilemma (and almost paranoia the more I think about it) is what happens if any of the joints leak once the tray is stuck in place as there will be no way of telling if this occurs unlike with the elevated tray we had before.

A thought I had, because the tray will be stuck to the floor with adhesive and sealed all around the edges with silicone, is to simply drill a hole in the side of the 110mm pipe to allow any water to trickle down therein. There would not be a smell issue because the tray is effectively “hermetically” sealed over the drain.

I just wondered if anyone else has come across this issue or has any ideas of how to allay my fears!

When you choose your decorative panels check the quality suits. I fitted some and when the light hit the panels you see the outline of the construction corrugation in the panels. The better ones have a ply back or other solid backing but are more expensive.

A way of ensuring the joints don't leak is to fill the void you have with a liquid screed of some description. That will ensure that there is no leak. Have never done it but that would be my approach in the situation you have. Does your tray sides have an upstand that will make sealing of your panels easier. I would silicon the faces of the tray that meets the wall as you put it in and then the joint itself before putting on the panels and seal it yet again. I found the best silicon is the Mapeisil AC. Last bathroom I did 8 years ago the sealant is still looking like new. Hope you have a lightweight tray as that will make the alignment of the trap and tray outlet easier that has to be spot on.
When you seal the glass panel to the tray seal the outside of the glass not the inside. Sounds counterintuitive but that was the best tip I had on fitting shower screens. Apologies if you know all this.

Thanks all three for your comments.

The wall panel supplier recommends panelling down onto the tray using the special trim provided which has an upstand on it, which sits behind the panel:
https://www.floorstowalls.co.uk/collections/trims/products/sealux-cladseal-strip

I'm not really happy with this approach as I have always been a fan of tiling right down to the floor as you can see in the photo. Much easier to remove a bath or shower tray with this arrangement!

In addition I will be using a self adhesive strip between the tray and the wall, and this itself has a thin flexible upstand:
https://www.plumbworld.co.uk/podium-shower-tray-flexible-seal-strip-18192-1256707?queryID=e9b6da646ca9ba8f04a28b2a2426a12d

Plenty of silicone to be used of course with both the above!

I have tested the pipework in situ as per in the photo and no leaks. I have also tested the trap separately in situ in the tray outside on a patio table as per a video I saw on YouTube and again no leak around the rubber gasket. It's just the thought that I wouldn't know if there was a leak once the tray is stuck down! The trap manufacturer (McAlpine) says that a neutral cure silicone can be used with the rubber seals if desired but I'm not sure about using it because how long would this material last I wonder? The test run was ok without silicone. Any thoughts on this?

I'm thinking of using a thin layer of self-levelling compound over the existing floor tiles (with a prior coat of SBR bonding first) to level the floor. It's not bad as it is, but is not perfectly level. Then use a cement based tile adhesive to mount the tray on. The tray manufacturer (Mira) recommends a dryish mortar mix (1:5 cement:sand) but a friend has used the former and found that to be good.

Phil, I take your thoughts about drilling a hole in the 110mm pipe – probably not a good idea! Just concerned where would the water go in the event of a leak, even if just a few drips but on a daily basis. You can see in the photo that the DPM is breached where the 110mm pipe emerges so I guess it would find its way into the sand blinding layer beneath. According to the building plans there is supposed to be Jablite insulation under there somewhere but I don't know for sure.

Revor, thanks for the idea of burying the pipework in screed but I don't fancy that. The 40mm pipe is stuck in the elbow at the doughnut end with solvent cement so should be pretty “bulletproof”. I have thought about applying one of those hybrid sealant/adhesive compounds around the outsides of the compression fittings at the trap end as a belt and braces approach.

Re: grab handle. Yes, we already have one. One of those fold-down types like the ones used in toilets for disabled folk. It doubles up as a towel rail!

Re: glass panel. Yes I know about sealing the only outer edge from previous experience. As you say it does seem counter-intuitive – I still don't understand why it has to be that way! I have the option of adding a small return on the end but we are going to see how the shower works first and if there really is a problem with water escaping from the tray. The return is almost as expensive as the glass panel itself!

Posted By: ArtiglioYou really need to think of the millions of traps, joints and pipework that have never leaked and likely never will, if it’s sealed now and put together properly , then not strained when the tray is fitted and trap/ outlet connected , it really is unlikely to leak. And as you say the dpm has been breached so even if there were a small leak you’d probably never know.

Yes, I know, my head says that's correct but my heart says be ultra-cautious here! I guess it's because this will be the first of the many plumbing projects I have undertaken where I will never be able to check/observe any leaky connections.

Can I ask - would you use silicone on the rubber seal between the trap and the tray or not? The manufacturer McAlpine states that if desired a neutral cure silicone mastic can be used but other pundits say they would not.

Posted By: Jeff BCan I ask - would you use silicone on the rubber seal between the trap and the tray or not? The manufacturer McAlpine states that if desired a neutral cure silicone mastic can be used but other pundits say they would not.

Posted By: ArtiglioJeff, i just put a bit of silicon grease on all the seals and washers these days,

It should be noted that silicone mastic and silicon grease are 2 different things.

I would go with Artiglio and use silicon grease.

Posted By: revorThe part that is the top of the outlet which screws into the trap looks like chromed metal but in fact it is chromed plastic......................It is a bad design chromed brass would be better.

Which would put up the price or put down the profit
And it's a competitive market place

Thanks all for your latest comments. The tray is now in place - see attached photo!

Artiglio - I went with your silicone grease idea. I did a fair bit of research on the type of trap to use and the McAlpine seems to be the one that is most highly recommended. It should be good for what it cost (nearly ÂŁ40)! The tray came with a trap but it was nowhere near the quality of the McAlpine so I opted for the latter.

Peter - yes, silicone mastic and grease different beasts entirely. The irony was I have the latter here already but which I have used for a completely different application (to coat rubber gaskets in my microinverters but that's another story!). Never thought about using it here for some reason.

Revor - the threaded top of the outlet that screws into the trap base is chrome plated brass and quite a solid beast. Hopefully there won't be any problems with that. I used silicone grease to grease the thread before putting it into the trap and this greatly facilitated the take-up. Cross-threading to be avoided at all costs in this scenario!

The beige coloured strip around the two sides of the tray is Flexiseal as belt and braces to seal tray to tiled walls.