Water leaking through tundish

[alwaysproblems]

Hi, I'm new to unvented hot water systems. Recently I've noticed water leaking through the tundish, it's almost a steady flow.

If I turn on the hot water tap for a few moments it stops running I'm guessingbdue to the drop in pressure. I wouldn't say the hot water is excessively hot.

The cold water mains pressure to my house is in excess of 7.5bar with no prv.l except the one on the boiler set at 6bar I think. Is this the likely cause of the leak?

I've got a plumber booked for the 20th September (earliest availability). Does this require attention before that?

Thanks for the help

 

[cross thread]

Yes it needs looking at asap, check plumber has the correct qualifications to work on unvented

 

[Johntheo5]

Hi, I'm new to unvented hot water systems. Recently I've noticed water leaking through the tundish, it's almost a steady flow.

If I turn on the hot water tap for a few moments it stops running I'm guessingbdue to the drop in pressure. I wouldn't say the hot water is excessively hot.

The cold water mains pressure to my house is in excess of 7.5bar with no prv.l except the one on the boiler set at 6bar I think. Is this the likely cause of the leak?

I've got a plumber booked for the 20th September (earliest availability). Does this require attention before that?

Thanks for the help

Have you got a set up like this on the cold mains which includes a PRV normally set to 3.0bar, a expansion relief valve set to normally 6.0bar, this is the one that should be passing into the tundish, if so you probably need the expansion vessel recharged or renewed but probably OK to use until your plumber has a look, if your system doesn't have this set up and PRV is lifting on the HW cylinder then I wouldn't use it.

 

[alwaysproblems]

@Johntheo5 I'm not sure, it's quite boxed in which doesn't make it easy to figure out what goes where. I've added some pictures, hopefully makes sense

I'll also add that I checked the water temp coming out this morning and it's hot water.

 

[Exedon]

Some one with a G3 ticket required sooner rather than later.

 

[Madrab]

Ideally you would install a Pressure Reducing Valve (PRV) onto your incoming mains and set it to 3bar. That pressure level will cause havoc with all the water fittings and fixtures in the property longer term. The Unvented is protected by it's own PRV but when it start to wear etc it can go out of calibration.

As suggested though, it's needs a qualified engineer to take a look and service the unit, part of that service should correct the issue you are experiencing.

 

[alwaysproblems]

Is it worth turning down the thermostat in the meantime? We have to wait a month for a plumber

 

[Johntheo5]

If the leakage continues after the heating period then the PRV (pressure reducing valve) is leaking past, if it stops shortly after the heating stops then the most you will lose on heat up is 3 to 4 litres after each reheat period if a a full cylinder vol reheat or 2 to 3 lires if a 1/2 to 3/4 cylinder reheat.

 

[alwaysproblems]

So I had a plumber out yesterday who repressurised the expansion vessel and replaced the valve which opened to spill however I noticed this morning the tundish is spilling again. What else could be the issue?

 

[Madrab]

1st thing, did you check that he was qualified to work on the unvented? He should have confirmed his UV ticket.
2nd, what was he there to do? He should have been there to service the unit, part of that would be to check and test everything to ensure everything is work as it should and adjust or change things as necessary. Therefore if it is still passing you could call him back and ask him to sort it.

Feel the water, is it warm or cool?

 

[alwaysproblems]

I live very remotely so kind of have to take what I can get.
He was there to resolve the issue.
Is it possible the thermostat could be set too high and therefore it spills when above 90c? The water this morning coming through the tundish was hot however, before the repair, in the evenings the water was cold despite there still being plenty of hot water from the tap. I can't comment if cold water is still being released as it was only repaired yesterday so hot water was drained.
Could this point to a faulty t&p valve? I've noticed this morning there is a small leak from the thread.

 

[Madrab]

That's where the question as to hot or cold. If it's hot/warm then that tends points towards the T&PRV possibly passing, if it's cold/colder then points towards the PRV but that's easily tested for.

The stat set high wouldn't allow the water to reach that temp (90Deg), most stats top out at around ~70deg, even then the system water that heats the HW shouldn't get that hot either unless the HL stats and HW stat are all faulty. Is it a gas/oil boiler or direct or other?

Ideally the chap doing the work should be running through a full service on the cylinder and that should encapsulate every control and safety device attached or connected to. If you had him out to fix the tundish issue and it's still running then he hasn't fixed the issue and throwing a relief valve at wouldn't be my approach. I would setup a test to check which relief valve is lifting but that needs it to go through a full heat cycle and for it to show one running before seeing which one it is.

 

[Johntheo5]

So I had a plumber out yesterday who repressurised the expansion vessel and replaced the valve which opened to spill however I noticed this morning the tundish is spilling again. What else could be the issue?

Which valve is this?, is it the 6bar expansion valve on the mains, after the PRV.

I live very remotely so kind of have to take what I can get.
He was there to resolve the issue.
Is it possible the thermostat could be set too high and therefore it spills when above 90c? The water this morning coming through the tundish was hot however, before the repair, in the evenings the water was cold despite there still being plenty of hot water from the tap. I can't comment if cold water is still being released as it was only repaired yesterday so hot water was drained.
Could this point to a faulty t&p valve? I've noticed this morning there is a small leak from the thread.

Can you just run off say 10L of HW, then, with HW heating off, do not use any HW for a few hours or do it overnight and see if water is spilling again, if so, most likely the PRV and almost definitely if the water is as cold as the mains.

 

[alwaysproblems]

Which valve is this?, is it the 6bar expansion valve on the mains, after the PRV.


Can you just run off say 10L of HW, then, with HW heating off, do not use any HW for a few hours or do it overnight and see if water is spilling again, if so, most likely the PRV and almost definitely if the water is as cold as the mains.

So he replaced the 6bar cold water prv. This must have been faulty given the water was at some points cold coming through the tundish. Surely the fact that the water this morning was hot suggests its the 10bar t&p valve near the top of the tank? It's not running constantly like it was before.

He's coming back Friday to have another go.

 

[Madrab]

I would disconnect both from the D1 out to the tundish and run them into individual containers, that would then give a definitive answer but that would be for him to do.
Did you check he is qualified BTW? Need to be to work on UV.