Another leaking unvented system!

[joeirish]

My unvented system is losing pressure. I have been checking to see exactly when this happens and it seems to be losing quickest when washing machine or dishwasher are in use. Pressure drops from just above 1 bar to almost zero over a period of a few hours. I have to bleed the towel rail (highest point of the system) every so often so must be a leak somewhere. The pressure stays constant when heating is on and when boiler is running and also stays constant overnight when there is nothing happening except or the ocassional toilet flush. I am just wondering what I should do to start checking. Thanks.

 

[moonlight]

Is that the pressure of the boiler dropping? Where are you reading the pressure from?

 

[Best]

Your radiators and heating boiler system are a different water system to your hot and cold water system.
So the toilet or washing machine for example, won’t have anything to do with the pressure in your towel rail.

 

[Scott_D]

Some pictures of your setup might help

 

[joeirish]

Thanks for the replies. Here's the thing. It seems to be OK now. No pressure los for the past 48 hours. So I'm trying to figure out what I have done over the past couple of days. The main thing is that on the heating circuit (we have ufh on the ground floor) the plumber has also connect a towel rail upstairs. Now there is a motorised valve but for some reason that has never been connected to the controller. So when the ufh is on the towel rail warms the upstairs bathroom. It is controlled by a thermostatic valve. I turned this down the other day and since then the situation seems to have resolved. So I'm going to turn it up again and see if this is what is causing the problem. I'll let you know and maybe ask what I should do next if this is the issue.
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Is that the pressure of the boiler dropping? Where are you reading the pressure from?

I'm looking at the pressure guage on the top of the thermal store. There is a cold water feed that can be turned on and off (the red tap on the left in the attached photo). I think that guage is showing the overall pressure because the way the plumber connected the system up.
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Some pictures of your setup might help

Attached is a photo of the top of the thermal store and the pressure guage.
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I was just taking another look and there are two pressure guages on the system. This photo shows the other one. Now I've only being looking at the one at the front and not the lower one at the back. Both seem to be on the same filling circuit.

 

[Best]

Auto vent is leaking. It will likely weep and then partly seal itself and then start weeping again.
Do not tolerate any signs of weeps at any valves or fittings.
Auto vents are notorious for leaking.
The wee plug cap on top of them can be used for to seal them manually, although that then prevents them venting automatically.
I rarely use them

 

[joeirish]

Auto vent is leaking. It will likely weep and then partly seal itself and then start weeping again.
Do not tolerate any signs of weeps at any valves or fittings.
Auto vents are notorious for leaking.
The wee plug cap on top of them can be used for to seal them manually, although that then prevents them venting automatically.
I rarely use them

Thanks for that. I there another type of valve I should have instead of that auto vent?

 

[Best]

Thanks for that. I there another type of valve I should have instead of that auto vent?

I find any type I have used can fail. Heat especially will damage them, such as those screwed directly into top of oil boilers.
Just replace it with a new one.
They come in different thread sizes though of commonly 1/4” or 3/8” thread with perhaps a bushing to 1/2” on some

 

[joeirish]

Some pictures of your setup might help

Here are a few photos I took today, I've labelled them as far as I can with my beginners knowledge! Also the manufacturers diagram of the top of the thermal store. We don't have solar panels so the plumber used these circuits for the boiler flow and return.
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Is that the pressure of the boiler dropping? Where are you reading the pressure from?

I've attached so photos to another reply in this thread. If you take a look you will see I've labled two pressure guages. I was taking my reading from PG1.
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Your radiators and heating boiler system are a different water system to your hot and cold water system.
So the toilet or washing machine for example, won’t have anything to do with the pressure in your towel rail.

Thanks, we have UFH downstairs and a towel rail in the bathroom upstairs. The flow and return for ufh manifold and the towel rail are all off the boiler flow and return which links into the coil in the thermal store. DHW is part of another system. What confused me was that I saw an immediate drop in pressure when the washing machine or dish washer were running but the pressure stayed constant otherwise. And both of these are only fed by cold water. Not sure if that would be significant. Anyway turning down the TMV on the towel rail seems to have sorted the drop in pressure. So maybe I was barking up the wrong tree.

 

[moonlight]

What cylinder is this? I don't recognise it and I don't see any pressure relief pipework for the heating? PG1 looks like its for the heating. Is there an expansion vessel for the heating somewhere? I can only see one for the water.

 

[joeirish]

What cylinder is this? I don't recognise it and I don't see any pressure relief pipework for the heating? PG1 looks like its for the heating. Is there an expansion vessel for the heating somewhere? I can only see one for the water.

It's called a Latento. Attached is a better photo showing the pressure vessel. 35 litre volume. The way it works is that the thermal store holds 500 litres. This is what heats the water in the DHW and UFH coils. The boiler flow and return are also connected to the ufh manifold which is not in these photos but is in one I posted yesterday.