ProDave

Tarmac you can drive on straight away even if still hot.

This is a good description of how the 3 port valve works http://wiki.diyfaq.org.uk/index.php/Three_port_mid_position_valve I still suspect yours is overshooting and not reaching a stable mid position "In the "water and heating" state, white is energised. If the valve has port B open, the motor will wind it until A+B, whereupon SW1 changes over, DC is applied to the motor via SW2, and it will stall. If it overshoots, or if it port A was open, SW2 will be operated as well, removing all power from the motor, and allowing the spring to pull the valve back to A+B. It is fun to watch this happening: as the spring pulls the valve back from A open to A+B, the motor acquires quite a momentum and overshoots. It then winds forward a little, and stops in the correct position." Check the voltage coming out of the orange wire. (boiler demand) I bet you will find it is pulsing on and off.

Or just wait until it next floods and it will be obvious which bit is sticking out of the flood water = that bit is too high.

Y plan = 3 port motorised valve. the work of the devil. I bet of you go and look when it is selected for DHW and HW, the 3 port valve has not settled in the mid position but is hunting backwards and forwards, and in the process the call for heat to the boiler is turning on and off. Replace valve control head or bin the 3 port valve and use two 2 port valves instead, FAR more reliable.

We only have the one triangular window in our sun room. It has no blind and never will. I would be very interested so see pictures or a video of any bespoke blind for this sort of window in use, ours have a 45 degree slope and I just cannot imagine any sort of blind or curtain that would actually work. But we knew this at design stage and knew there would be no blinds needed on this window.

That is more or less what I did with my electricity connection.

Looking at that drawing above. What height difference if any is there between the treatment plant and the soakaway? Can you add to that drawing or produce another one showing what happens at the "output" of the soakaway, including levels of important features.

Two points here. The 2 houses feeding this with septic tanks should not do that any more. But sadly SEPA don't seem to care about old non compliant systems. So on the face of it you have a soakaway and rubble drain acting as a partial soakaway and ending up in a burn. So in theory this should never back up to the point of flooding the treatment plant. So something is wrong with the levels when it was installed that is causing the plant to flood, or something is blocked. THAT is what you need to concentrate on finding, what is the weak link in this that is making it possible to back up. Probably an unpleasant job of paddling about in wellies next time it does back up to work out where the problem is. It surely should not be hard to sort out when you have found it. With an eventual destination of the burn, it should not normally back up.

Fred Dibnah was on television several times filling his boiler from them and telling us it was illegal to do so. I wonder how many times he got fined?

Can you post an actual model number of the thermostats, there must be something on them somewhere?

A friend of mine bought a house like that. He had a survey during the buying process and the surveyor warned the corner of the landing like that was cantilevered from the rest of the building and was a structural defect. My friend of course answered, well it has not fallen down or even moved in the last 60 years so I think it is okay.

It sounds like an RF interference issue, or the non working stat has become faulty. Does the manual say what frequency they operate on?

Yes I too fitted a pressure reducing valve to protect the (not fit for purpose) lousy plastic pipes and fittings used on my 'van.

That has narrowed it down. Are the wireless stats mains or battery powered? If battery can you physically move it closer to the WB9? Have you checked the state of the battery? how far away is it? Any thick walls in the way? Any NEW equipment added like new wifi router?

Replace with your own system assumes you have enough land to do that. Often a shared system is because you don't, especially if they have bodged the soakaway. I am hoping @BigYin will come back and tell us more please.

If it is condensation, then I would expect it to have dried out completely over the summer as the walls will not be cold enough to be below the dew point. Do NOT invite a "damp specialist" around. I have yet to hear a good outcome from that.

How does that work? Do they fit a separate meter for the heat pump? It sounds like hark back to the "total control" tariff that gave cheap rate 24/7 for heating appliances but that had it's own meter for that.

Can you clarify is the floating corner the bottom string going down to the ground, or the upper string going upstairs? If the downstairs one as the drawing suggests to me, then the dod leg stringer joint will be in compression so the hidden fixing might be less difficult, but that will rely on the bottom of the stringer being properly fixed to the floor so it can't move and spread outwards.

First thing to check is on your WB9-RF when a zone calls for heat is the LED on the controller for that zone light up? If not the problem lies with the TF thermostat for that zone. If the LED is light up, the RF thermostat is working, next check is the manifold pump running? Is the 2 port valve for the UFH energised? Report back.

Fit another door frame inside the one that is there? Will the architrave cover both if you do that? Do NOT use the same joiner again. I would be asking why HE made a unilateral decision to fit non standard frames thus forcing you to buy non standard doors. and suggesting the easiest way to remedy HIS mistake is for him to come and convert them to standard size at his expense. 2040 is the tallest "normal size" That is what we have from XL Joinery, very good doors. It sounds to me like he did not think, he fitted door frames to fit the structural opening which is usually over sized, rather than fitting standard sized door frames with appropriate packing to fit the opening.

I suspect the only way is a steel structure hidden behind the stringers to give the strength. To me is seems a lot of extra work to avoid one newel post going down to the ground at that corner.

Post some pictures of your wiring centre and the UFH manifold and in particular did they install any 2 or 3 port motorised valves when fitting the system?

What type of render? That air brick needs cleaning off and the holes unblocking.

You can buy a complete air blower pump for not a huge amount, this one seems common in treatment plants https://www.ebay.co.uk/itm/296023440964 A new SWA cable will sort out your electrical woes, even laid on the surface until you can bury it. BUT until you solve the drainage field issue, it will continue to flood, and when it floods is when the raw sewage can float over the normal weir separating input and output. That is going to cost you money as you basically have to dig up a large area of land and re lay a proper drainage field separate to rainwater soakaway. Sorry to say you are picking up the fallout from the original builder that did not do it properly. It there a watercourse nearby? If there is seeking permission to discharge to that would be a much better solution. The people advising to change for a mechanical treatment plant are simply not understanding that the fundamental problem you have is a drainage field that cannot cope so it floods. Changing for a mechanical tank (not recommended) would only solve your problem if the drainage field was re laid properly as well. How old is the house? Did it come with any form of 10 year warranty? Is there a legal agreement to force the other house to share costs?

I say you definitely need a plumber to sort this out for you, you don't want to be making a mistake and connecting water to the boiler gas supply, or worse, gas to the cold taps. There is probably a gas cooker as well. Following the pipe from that should confirm which is gas. If the WM tap is the gas pipe then the previous "plumber" is a cowboy.