Nickfromwales

@Dee, who fitted the boiler and did they flush it?

You can use cable ties and bases on things like MVHR ducts, as they’re not heavy, but obvs no good for soil pipes etc. No specific regs afaic, just more common sense and a robust approach to resolve this. Soil pipes need clips or banding, and as water changes direction you need to arrest any movement that would eventually cause a fitting to come away from the pipe. Water pipes have clips for the pipe size, so easy solution there.

The top rail of the manifold has flow meters which show litres per minute per loop. When running, can you see these moving and what do they show? The hope would be that the ones for the rooms not heating up would show no flow, meaning you have airlocks or a poorly balanced setup that needs tweaking. The worst outcome may be that the actuators on the bottom rail have snuffed it and are no longer opening the loops to the affected rooms. Any info on the first question re the flow of water would be a good place to start.

Crikey! That’s a very complex arrangement. Could you take some pics standing a bit further away so we can see what’s what? Thanks.

Any reason to flush? You’ve drained this down a number of times and have some new valves here and there? Water still grotty, or just cool spots on rads?

Yup. KISS wins every time mate. Tbh you’d be opening up a giant can of worms if you went opening up / disturbing bigger sections of ground near existing founds to drop pads in afaic, so glad that sense has prevailed here At least underpinning can be controlled in smaller sections.

I’d go for the single location, wherever, with a larger lower temp cylinder, and a secondary hot return circuit which was insulated very well; this is what I do on most jobs and works a treat. When you get used to near zero wait time for premium temp DHW to come out of the tap, you’ll not go back to tolerating the wait. If there’s solar or cheap lecky to use to offset the small uplift in energy costs to run this system then it’s a very nice luxury to have and doesn’t cost a lot. Place the money saved from the 2nd cylinder ( labour / materials etc ) into a glass jar, and use that to pay the energy bill.

Dont you just want to catch this crud at the unit filters, vs climbing up and getting fingerprints on the room vents? Unit filters are cheaper than shoplifting so why add the ballache of having to micro-maintain this?

Only the most pedantic BCO will ask for it to be at the very end of a run, so if that’s not practicable then just say you have an SVP and keep the details to an absolute minimum

I got done like a kipper fitting one a couple of weeks back lol. Was looking at the symbols from the back of the unit and my poor little brain didn't allow me to mirror it. An hour or so of swearing and looking like a tit in front of the client, and all good. Noticed just after I had finished fitting the self adhesive neoprene insulation to it...ffs. 🥲😭🥲

Why are you wasting room with mats when you can just clip directly to the P5 deck (floorboards)?

I’m saying you don’t have one run with a WC on the end and another further down the same pipe, you have 2 pipes, one in each room. Therefore you can ignore my corner branch as I mistakenly thought you dropped in the corner that side. Can you dril through the wall and connect the WC closest to the SVP into the horizontal run of the other WC?

Ah, cool. Picture speaks a thousand words, and all that jazz. The fitting in the corner will need to be one of these https://ebay.us/m/ICnVBo You don’t have 2 WCs in one 110mm line so my previous about Y branch can go away. All good with 90° bends (bent pan connectors) and straight runs. For the double corner branch, just order a cleaning / rodding eye (access cap) to push into the top outlet to close it off.

In isolation I’d use S&C for strength and longevity.