ProDave

Yep, if no services, put the PB straight onto the PP board without a gap. Gives you a little more heardoom.

post the details of the exact thermostat.

Surely a utility room will have a sink unit or something, put the odd ones under there?

You should have counted how many you had before you started that room.......

Tile the WHOLE utility room different. Keep the rest of the white ones as spares for the other rooms.

We have a petrol leaf blower. It can also suck and act like a big vacuum cleaner sucking leaves up into a bag. That function is handy for clearing out gutters and drains, but not of much use for general leaf clearing as it would be soon overwhelmed.

Heating the hot water will heat it hotter than the ASHP so there will be more expansion. But that should not be a problem. You have two expansion vessels for the hot water, I only have one, and my single expansion vessel is still working fine. If you wanted to keep the 2 old ones you could refurbish them with a new bladder in each, or even ask they guy if he would replace the bladders for less than the cost of replacing the whole thing?

Okay progress. We know the hot tank is over pressurising when the water is heated which does indeed usually indicate the expansion vessels(s) have failed. I am a little surprised as there are two of them so would expect them not to be particularly stressed. This is not something to ignore. You have to trust your gut feeling and get the person that quoted to replace them or a different plumber that comes trusted or recommended by a friend. This does not need to be a heat pump plumber as these expansion vessels are the same regardless of whether it is a heat pump, gas or oil boiler, or just plain direct immersion heated. Switch off the solar diverter for now and only heat the hot water occasionally as needed using the heat pump to heat it. A lesson here is be there when the next plumber comes so you can engage with them and when they find a problem like this they can probably show you what they are testing that made them conclude they need replacing. One would hope they had de pressurised and concluded the air bladders are burst and they would be able to show you. EDIT: to add to the above post, if you have a car pressure gauge and a bicycle pump we could talk you though checking the pressure to be absolutely certain if they have failed or just not enough pressure in them.

I very much doubt you will get two 10mm cables into one of the terminals on one of those. Is this a (home made?) storage boiler? the commercial ones will have one high power feed to a control box and typically use a contactor to switch each element.

Before you make the choice, price up all the options. Frametherm is so much less nasty than most wool insulation and it is quite stiff so when pushed in place it should stay there while you get the netting etc in place, many will just fall out. https://knauf.com/en-GB/p/product/frametherm-r-roll-35-ready-cut-26329_4206 Search for best price, I got mine from SIS as they were the cheapest I could find it at the time.

4" will be a lot better than nothing. It will be a miserable job from below you will need full suit and respirator imho. Use something like Frametherm 35, a lot less nasty than most flavours of rockwool style insulation and quite stiff so should push into place and stay there while you get the netting in place.

Where I worked before they built a spiral staircase. The plasterboard was stood against a wall outside and wetted frequently and gradually it curved under it's own weight as it was leaning against a wall. After several days it had got to the approximate bend radius needed so it was brought inside and wetted further and gradually eased into the bend needed. Once to the radius you need you let it dry before you screw it to the wall. That is a job well suited to DIY as it will take time and your own labour is free.

More information on what wall finish you have, and what sort of access panel you want to make.

He says he topped up the glycol levels so that makes sense.

Yes that is the tundish. It should remain bone dry. IF any water passes through it would pass on the inside, it is just there so you can see if anything is passing through. You could try rolling up a bit of tissue or toilet paper and sliding it into the space inside. That will show you if there is any discharge even when you are not watching it. It that remains dry over a few days as you use hot water and it gets re heated, then there is nothing wrong with the white expansion vessels.

"servicing a heat pump" might be slightly specialised, but just about any plumber should be able to do all the normal things related to the rest of the system like expansion vessels pressure checks etc. Those would all be the same if you had a gas or oil boiler as the heat source. So it looks like the red heating expansion vessel is okay. Just the 2 white ones to check. Can we have a photo of the pipework under the tanks? We are looking for a Tundish that will look a bit like this When you find something like that, have a close look at it. If there is a problem with the 2 white tanks that the plumber wants to change, then whenever it heats the hot water, you will see water dribbling down the inside of this. It should be bone dry normally.

I had similar with the flashing for my stove flue that bent up one corner in a storm. My repair was to bond it down with appropriate goop. Has not happened again.

Why not dig up the flower bed, install a proper soakaway under the flower bed then put the soil and plants back?

Just see how it goes for now. Check next time the heating is off and all cold (first thing in the morning?) and see if the pressure has stayed up or gone back down again.

That's why I am suggesting @canalsiderenovation does some investigating of her own with our guidance.

Quite apart from the issue of the gap may not have been pulled tight all the way, to me it looks like the joining strip may have been cut too short and it seems to end above the bottom of the window. That might explain the daylight you can see?

Oh you have 3 in total. The red one will be for heating, that is your one with the immediate issue. The TWO white ones are for the hot water. There is no indication that there is actually an issue with those yet. The fact this guy suggests replacing the 2 white ones but has not addressed the low pressure on the red one has done nothing to give me confidence in him. Lets tackle each separately. The white ones don't have a pressure gauge, they will be at mains water pressure. They are to take up the expansion when the water in the tanks gets heated. IF they have a problem, you will see water being discharged via the tundish after you have say had a shower and used up some hot water and the cold water that has entered the tank to replace it is being heated. If you want help identifying what the tundish is, post a picture of the pipework below those tanks. A further note, those tanks are of the type where you can take that bottom flange off and use that access to replace the bladder if it has burst. But I suspect the labour charge would make that more expensive than just replacing it, if they are faulty. Summary. If you just accept that quote, you will get 2 shiny new white tanks that may or may not be faulty, and the low pressure on the red one will still be the same.

They should not fail that regularly. Do you want to do a few checks with us to really determine has it failed, or does it just need the air pumping up? If they do fail regularly it might be a sign they are too small. What size are the ones there? We have only seen one of them so far where is the other one?

https://www.screwfix.com/p/flomasta-potable-expansion-vessel-24ltr/131kk £40 each from Screweys, so that makes it £310.40 for labour (including the VAT) How long did they say they would take and how many people?

When booking the next person, say you want a "G3 service" If they mumble, pause, or say "what" they are not the right person. Before that, when the system is next cold and reading 0, you could try reading the pressure at the valve on the top with a car tyre pressure gauge and tell us what reading you get. It might just need topping up.