Nickfromwales

Cost for one, ugly as shit for another, lol.

Compression stuff is very good tbh. Fire away. Just have a reality check about where these go and if you’re ever going to actually dismantle them, ever, and if not then go for solvent weld (permanent) there and only fit compression where you think it’s a possibility that you’ll need to fettle retrospectively.

Push fit waste fittings are the last thing I’d use. Solvent weld is bombproof. Try a few test joints with solvent weld, as it goes off in seconds and offers no room for ‘tweaking’ , eg if you’re a novice and have not done this type of plumbing work before.

Respectfully, this doesn’t sound like a small job unless it’s 1x door and 2x windows? How many units in total need to be removed and replaced?

Yup, +1. I've done plenty of these types of installs and with exactly the methodology described by the OP, never an issue. IMO the underlaying concrete (that most builders knee-jerk to without any thought) is a waste of money. This is absolutely reliant on the preparation works and that having been done meticulously without divots or voids in the sub ground / earth. Last one I did was 200mm of PIR then 85mm or so of dry screed with 16mm UFH pipes stapled to the insulation. I don't really bother with the top 'membrane' and I've never had any issues. I once had to do an insurance job where I had to take an Everest conservatory floor up (tiles were cracking and floor screed caving in) and they had done this methodology, just very poorly prepped and loads of undulation in the ground prep. The screed was laid directly onto the PIR and all that happened was the foil had tarnished a little, over 5 years or so. I'd only go with the upper membrane if going for a true liquid screed.

@craig may be able to help with some names etc? He's a BH 'trusted member'

@craig about these days?

Can you clarify, are you needing a fitter to remove all the already installed units and then install the replacements (and for the new team to first of all survey and place an order for the replacements)? Please give as much detail as you can

Great, no probs For any of the runs off 110mm I would defo use 50mm until at the room or appliance, and then reduce down when it is above ground / in wall / exposed etc where you can then get to it. I never bury 40/32mm pipework, unless its the very short bit under a shower trap and that's a factory fitting which won't take 50mm directly. Use solvent weld PVC vs push-fit too, as they aren't reliable IMHO. If the kitchen sink drops less than 1300mm before going horizontally to the second drop, then to 110, then you'll probably not need an AAV at the kitchen sink, but I think I'd put one in for Justin (Justin Case) to be belt & braces. If you've an appliance (dishwasher or washing machine) in the kitchen then don't connect via the sink trap appliance connector as that's noisy to the room when pumping out. Fit an appliance upstand instead, tee'd into the kitchen sink waste pipework eg after the sink trap. Much better job. https://www.screwfix.com/p/floplast-washing-machine-trap-white-40mm/18640?tc=ET2&gad_source=1&gclid=Cj0KCQiA7se8BhCAARIsAKnF3rwrmETQqq319b3N-BPY_d3gqzuT1HRwstHyu0gi6IZk5EPTp69VC6kaAvObEALw_wcB&gclsrc=aw.ds One for each appliance.

Have you asked the BCO to attend to get input from them? In certain adverse conditions they will allow a deviation from “written law” and allow you to then demonstrate that it functions well / is reliable in operation, and then sign you off. What is in the bible is often difficult to achieve (to the letter) in real life and in every situation, especially if it’s a retro-fit / alteration. Speak to them and get their input on what will / won’t be acceptable.

A bucket trowel is my weapon of choice, plus also a gauger for smaller areas that require a bit of control.

Hi. If the invert, the lowest point of the outlet of the WC and the lowest point of the horizontal foul pipe discharging to the sewers is less than 1300mm then you won’t have any issue whatsoever. The only way water gets sucked out of traps is by the flush water etc dropping a full storey of a building, vertically, and then there is a vacuum created behind it due to velocity. That’s when you need an air admittance valve above it to compensate for / neutralise the vacuum. Looking at your pic you have less than 1000mm invert(?) so the flushed water will simply not be travelling fast enough or for long enough a drop to create any vacuum. The only problem I see is with the pipe rising to a kitchen sink which will defo need an air admittance valve at its highest point (and where it is accessible), and I would do that run in 50mm pipe and fit a 50mm AAV vs 40mm (due to food waste & solids etc). Be sure to use bends not elbows on that pipework run too, so that run can be retrospectively ‘rodded’ with ease if a blockage ever occurs. Is that run more than 3000mm?

10 - 4, rubber duck

Any reputable cement board. How will you be fixing them to the structure?

Maybe the extra heater is a little OTT? Would it not be ok to just use the Sunamp / Thermino, and IF it snuffs it again you just replace it with an UVC and be done with it? That’s what a member on here did, eventually, when he realised he was seeing a SA repair & replacement engineer more often than he was seeing his wife…..

Excuse me, there's WAAAAAAAAAAAAAAAAAAAAAAAY more to it than that. I'll go google it now, gimme 5...

Defo. Have you removed it inside & out? I'd recommend getting up there and seeing if it is 100% gone.

I think its here, just check to be sure. LINK

The pic of the ceiling shows evidence that possibly loft insulation or a flap of felt / membrane is causing trouble. Have you been up there to investigate? Damp / mould down below just looks common to ‘life’, so will probably disappear with some ventilation.

Back when @ProDave was a boy, there was only 2 houses and a church

If you remember, I mentioned walking past the house with the shark through the roof. Lol. Just a couple of streets over from that.

Hi and welcome. I worked on a replacement dwelling in Headington, and I have to be honest it is just great to see old, inefficient bags of 💩 from an era gone by being razed and replaced with something great. That was an ICF build. Are you allowed a 2-storey replacement or 1.5 with room in roof / other? Bungalows seem (imo) such a waste of a good bit of ground space.

PM me if you want details of a great SE, (as they don’t want to be ‘advertised’). Not the cheapest, probably mid/high on costs at a glance, but they did a big complicated project for me and I was glad to hear there were no bolt-on costs for the good few final tweaks / redesigns etc plus they problem solved a bunch of stuff for us too (including coordinating with me for a large pita basement and swimming pool). Im glad you went with an insulated raft as these are night & day better than most other options

No mate, that’s exclusively reserved for us plumbers

May be of interest, that I fit Willis heaters in parallel in an infinite loop, with flow and return to the emitters taken off that loop a-la close-coupled tee arrangements. Much less stress on the pump when the TMV on the UFH manifold is close to or at the chosen set point.