Nickfromwales

You can turn the T and still get a thin rod up to the bath, so no worries there. Water will come out of the WC pan before it gets anywhere near that high, but rule of thumb is as you show. 200mm is plenty, but you can go higher, just no point afaic.

This!! A decent (👀) architect will be doing the brunt of this, and basically NOT designing a house that they know would rock the boat. If you push the envelope then the planning consultant is your new friend. But not until then.

I do like this forum. Some very useful information , and real life feedback here. Thanks for the additional detail @TerryE Tres bien. 👌.

Boilers usually have the trap inbuilt . I’ve fitted more gas boilers than I care to remember, and we’ve never had to fit a 3rd party trap. And yes, your pic is spot on.

The pipe off the 110mm should be 50mm up to where it heads in to the bath, turning in on a T with a rodding access (cleaning eye) for maintenance. From the 50mm T you reduce to 40mm to get to the bath T, and then the 40mm pipe continues to the boiler. That then terminates at a 40mm T with the centre of the T having a 40 > 21.5mm reducer in it for the boiler condensate, and a 40mm air admittance valve to complete the run. Absolutely ZERO need for a GSR plumber, this will just add wasted expense.

If you’d have said that earlier, I’d have said don’t dab! Metal frame saves the day (or timber) at that depth.

Tough for them. Tell them you’ll be using insulated closers and then they WILL be using brackets, as per the rest of the world! Stop asking them, and tell them. For hefty bifolds this is the standard way to get a solid fixing.

No. The pipe running from the UVC / hot manifold is direct to the outlet. The HRC pump is on the return, at the UVC, so has no effect on the delivered lpm. Sizing the pipework is critical for differing distances from the plant / UVC, and working out which outlets are needed most frequently etc, so needs a bit of thought, but a good design will reap excellent results. As stated above, even taking the return off at a point not immediately behind the outlet has significant penalties, and my thoughts are why the feck go to all this trouble, cost etc and still suffer any kind of compromises?

I was an exhibitor for 5 years, and a huge amount of people got to me, after all the sales BS had been deeply embedded in them, and then (as a consultant) they got to speak to me in an impartial setting. Most left me and shook my hand, saying thanks for showing them how to filter out the crap they’d just been subjected to, by themselves. How can 7 different ASHP or MVHR suppliers all be “the best one on the market”…..? Ask them to prove it, and then they start sweating. I got approached by a mass home developer after I was recommended by an ICF supplier, to support with a ‘new direction’ they were exploring. Building with ICF, going airtight, MVHR as standard (only for exclusive offerings £750k and up iirc), but when I stated Part O, cooling, and that can of worms was placed on a cooperate table somewhere, that all went stone dead; the sausages just kept falling out of the factory and they were being snapped up by folk who didn’t know any different, so they had no interest in changing course or doing things better. If nobody is demanding it, I guess there’s hesitance to supply it.

Scrap the bigger trap, move to a P or bottle trap, enjoy life with a job well done. Traps are easy to ‘self clean’, so it’s no biggy.

I’d just say beware of anyone who is partisan because they’ve used one system. I’ve been fortunate to work with multiples, warts and all, so am giving a balanced and real life overview from hands-on experiences.

Respectfully, nobody puts a 40mm trap on a 32mm sink. Agreed, they should have just said no, but sales always starts with a “yes”, and the let down follows after a lot of laborious provocation.

I wasn’t referring to damp issues, just that during the construction phase there was a lot of rain that made its way indoors, or had soaked into the lower sections of the interior woodcrete leaf. Not an issue with EPS, but it’s less DIY friendly (depending on what block you go for). I'd steer well clear of Velox, had loads of blowouts with that.

Just reduce 40>32mm at the point these two meet, and fit a smaller trap? That’s what I do, as I never run long lengths of 32mm pipe for basins any more, always 40mm and then reduce at the bend where it turns from vertical to horizontal. I use a 40mm 90° bend with a 40>32mm reducer glued into the bend, and then a short piece of 32mm to an 1.5” trap. Simples. You can even just buy an anti-siphon 1.5” trap.