New house plumbing problems

[gotomuzzi]

Hi all, new house has an oil boiler in the utility and an unvented cylinder in the room above it. About a week ago I noticed water trickling out of a drain pipe outside, when I went up to the tank I could see water flowing slowly through the tundish from the PRV up above it. Pulling the PRV knob stopped the flow so I thought that was the end of it.

Girlfriend phoned me yesterday to say water coming out of the tundish and through the ceiling, I asked her to switch HW off and run the hot tap for a while and it stopped the leak.

So I’ve got two problems, water passing PRV and tundish drain blocked. Am I right in thinking if the expansion vessel doesn’t have air in it then that might cause the PRV to pass water? But would that be more than a drip?
It hasn’t been that could lately so I don’t think the drain can be frozen, I’m not sure how else the drain could have become blocked though. Would a plumbers drain snake from the outside up be the best way to go?

I’m away with work for another week and if needs be I’ll get a plumber in but if its something I can fix myself then I would prefer to do that when I get back. Any help would be greatly appreciated.

[royceybaby]

Found this video the other day that gives an explanation of how unvented cylinders work: https://www.youtube.com/watch?v=1ZBeott7tE8 it may be of some help diagnosing.

If you have water coming out the tundish, something is not correct and needs looking at.

[silversurfer1]

gotomuzzi said:

Hi all, new house has an oil boiler in the utility and an unvented cylinder in the room above it. About a week ago I noticed water trickling out of a drain pipe outside, when I went up to the tank I could see water flowing slowly through the tundish from the PRV up above it. Pulling the PRV knob stopped the flow so I thought that was the end of it.

Girlfriend phoned me yesterday to say water coming out of the tundish and through the ceiling, I asked her to switch HW off and run the hot tap for a while and it stopped the leak.

So I’ve got two problems, water passing PRV and tundish drain blocked. Am I right in thinking if the expansion vessel doesn’t have air in it then that might cause the PRV to pass water? But would that be more than a drip?
It hasn’t been that could lately so I don’t think the drain can be frozen, I’m not sure how else the drain could have become blocked though. Would a plumbers drain snake from the outside up be the best way to go?

I’m away with work for another week and if needs be I’ll get a plumber in but if its something I can fix myself then I would prefer to do that when I get back. Any help would be greatly appreciated.

yes the expansion vessel being low can cause more than just a drip as the cylinder heats up.

Turn off main open hot taps until water stops, open prv keep open if poss. Attach foot pump to valve on expansion vessel and pump up to 3 bar close prv and turn main on and vent hot taps. You want 3 bar in expansion whilst 0 bar on outlet so keep taps and or prv open

the tundish pipe work probably is not blocked you can test this by carefully pouring water down it. Often what happens is the water is running to fast to get it all in the tundish and some makes its way down the side of the pipe rather than inside the pipe \(crap design)

Good luck

ss

[Walter E. Kurtz]

Good advice ^^^

Some would say that working on unvented systems requires a 'G3 ticket', but - as with all plumbing - it's not that hard, really.

It would be instructive to fit a 10bar gauge to register system pressure - if one does not already exist.

[Black_S3]

silversurfer1 said:

yes the expansion vessel being low can cause more than just a drip as the cylinder heats up.

If this is the cause then I think generally it will only happen for a short while after the system has been repressurised.

OP - I take it you've checked the most obvious that the filling loop isn't connected & letting through?

[Walter E. Kurtz]

Black_S3 said:

OP - I take it you've checked the most obvious that the filling loop isn't connected & letting through?

I'm pretty sure that isn't the cause

[Black_S3]

Walter E. Kurtz said:

I'm pretty sure that isn't the cause

Why's that? Have i missed something blindingly obvious?

ETA yes I have... boiler not even in the same room lol

Edited by Black_S3 on Wednesday 9th January 22:24

[Walter E. Kurtz]

The OP is referring to an unvented hot water cylinder, not heating system. Apologies if my comment sounded sarky - it wasn't meant that way!

[Black_S3]

Walter E. Kurtz said:

The OP is referring to an unvented hot water cylinder, not heating system. Apologies if my comment sounded sarky - it wasn't meant that way!

no worries I'd assumed both shared the same pressure release waste.

[gotomuzzi]

silversurfer1 said:

gotomuzzi said:

Hi all, new house has an oil boiler in the utility and an unvented cylinder in the room above it. About a week ago I noticed water trickling out of a drain pipe outside, when I went up to the tank I could see water flowing slowly through the tundish from the PRV up above it. Pulling the PRV knob stopped the flow so I thought that was the end of it.

Girlfriend phoned me yesterday to say water coming out of the tundish and through the ceiling, I asked her to switch HW off and run the hot tap for a while and it stopped the leak.

So I’ve got two problems, water passing PRV and tundish drain blocked. Am I right in thinking if the expansion vessel doesn’t have air in it then that might cause the PRV to pass water? But would that be more than a drip?
It hasn’t been that could lately so I don’t think the drain can be frozen, I’m not sure how else the drain could have become blocked though. Would a plumbers drain snake from the outside up be the best way to go?

I’m away with work for another week and if needs be I’ll get a plumber in but if its something I can fix myself then I would prefer to do that when I get back. Any help would be greatly appreciated.

yes the expansion vessel being low can cause more than just a drip as the cylinder heats up.

Turn off main open hot taps until water stops, open prv keep open if poss. Attach foot pump to valve on expansion vessel and pump up to 3 bar close prv and turn main on and vent hot taps. You want 3 bar in expansion whilst 0 bar on outlet so keep taps and or prv open

the tundish pipe work probably is not blocked you can test this by carefully pouring water down it. Often what happens is the water is running to fast to get it all in the tundish and some makes its way down the side of the pipe rather than inside the pipe \(crap design)

Good luck

ss

Thanks, that gives me some things to try when I get back.

[gotomuzzi]

Just to update this thread and thank everyone again. Got back today and silversurfer was right the tundish pipe wasn’t blocked at all it just can’t handle much flow and dribbles down the pipe. Next I did as suggested and drained the hot water and checked the expansion vessel - no charge at all so I have pumped that up to 3 bar with my foot pump which was easier said than done! So now I’m going to have a beer and watch the tank like a hawk while it heats up.

Cheers
Chris

Edited by gotomuzzi on Tuesday 15th January 16:51

[silversurfer1]

Good Man !

ss

[g7jtk]

Check that the expansion vessel is fitted in the correct place. If it’s not it won’t work. As the water heats up it expands. The only place it can go is through the pressure relief valve.

[gotomuzzi]

Well I woke up this morning to find it has leaked overnight. I’ll check the expansion vessel again to make sure it hasn’t lost its charge. Failing that it’s probably time to get a plumber in.

[g7jtk]

Post a picture of the area around the pressure reducing valve and the expansion vessel please

[gotomuzzi]

Quite difficult to get it all in shot, Is that the pressure reducing valve underneath the expansion vessel? Not the neatest of plumbing jobs but I think the house has had a few additions over the years.

[gotomuzzi]

Bit late in updating this thread but after some instructions from a plumber we worked out it was the combination valve that was causing the leak so this has been changed and touch wood no leaks since.

[dhutch]

The valves dont last for ever, same with the PRV's and the bladder in the expansion tank.

If it was flat as a fart, there is a decent chance it leaks a bit, and at some point will need refilling and or replacing again.

Sadly as you have found, its not at all uncommon for the tundish to fail in its hour of need.


I have been through this with my parents and girlfriends tank, both needing a new PRV and tank at around 30 yo, and will be making sure when we have our new tank put in at our own house there is a tundish arrangement that can take the flow of a running valve!


Daniel