Hi, I'm new here so please be gentle with me,I have probs with my glow worm 30 sx boiler, I keep losing pressure with water dripping throu the tundish, my plumber today replaced the PRV but it's still leaking . any ideas please.

What does the pressure rise to when the heating is turned on, say starting at 1.3bar cold.

The plumb er should have checked it and the expansion vessel.

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0.9 cold going up to about 1.3/1.4 when running. what pressure should the expansion vessel be set at?

1.4 bar wouldn't trigger the PRV! Are you sure he replaced it?

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Your problem is now our problem

Did the plumber actually change the pressure relief valve or just play with it, they seldom reseal once they are set off.

If it's a new one, then it's either duff or the pressure is rising to above 3 bar.

best to get the plumber back to have another look

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No he deffo change it, I never left his side, I actually think I've got other problems, got home tonight and towels under boiler( in airing cup'd) were wet so leak is in boiler? Also water passing throu' tundish is stone cold so is this coming from elsewhere, PRV's from mains supply, pressurised cyl and boiler are all connected to same tundish.

Got any pics?

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Your problem is now our problem

Agreed some pics would be useful

Could it be the cylinder letting by, the make and model of that as well please.

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Wierder and wierder, all seams OK this morning, we are away for weekend so will see sunday evening.
Thanks for your help.
P.s. cyl. is Telford tornado.

Right so the problem is most likely to be the cylinder.

It has an internal expansion vessel, follow the instructions to reinstate it or get a plumber with a G3 unvented qualification.

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Have ordered a new expansion vessel. old one will not hold pressure (tried pumping it up), also having a non-return valve fitted on hot out of cylinder. how much should I pay for vessel? telford exp19

Would sooner see a pic or two and there shouldn't be a non-return valve on the hot out.

Are you meaning the white vessel.

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Ive seen lots of nrvs fitted on the outlet of UVs where the cold supply isn't taken off the balanced feed from the valve. Then someone fits a cheap mixer and the pressure backfeeds to the cylinder.

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New expansion vessel and check valve fitted today , so far so good ( insert fingerscrossedsmiley)
Cant locate leak in boiler but seems to be coming from black plastic manifold only a very slight drip takes about 3days to drop enough to stop boiler working. Got a piccy to upload but dont know how to.