[Help] High pressure in boiler and constant leaking from overflow pipe

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Hi All,

I am new to this forum and hope someone can help me to identify what is wrong with my boiler and what I should do next.

I have a boiler downstairs (Mynute 28e) and a hot water tank (Flamco 210L) upstairs, as well as CH system. Both of them are around 15 years old.

A couple of weeks ago, I noticed that water (hot, when system is on) was constantly dripping (it can fill a wine bottle in a minute or two) from the overflow pipe outside the house. There appeared to have very slow dripping from the same pipe inside the house at the bottom of the boiler. Then I checked the boiler and the water pressure shown there was always at 3 bar. Apart from that, everything worked fine (CH and HW wise).

Because I had to leave the house for a couple of days, I turned off the main valve (so no water came into the house). After I came back, the pressure on the boiler became zero.

I have a boiler cover with my energy supplier so I called them for an engineer visit. The engineer arrived today and did some checks for me:

1) He opened the boiler and turned on a valve inside to release the water from the system into the overflow pipe, and the pressure went down, but then climbed back up again.
2) He went to the hot water tank, and checked the filling loop (which was properly closed). He even showed me by disconnecting the pipe from the filling loop and there was no water coming out.
3) He then turned off the inlet valve (cold water) to the tank. And came down to release the pressure, the pressure still climbed back up.
4) Then he turned on one of the hot water tap, the pressure seemed to be stable. But once off, the pressure would go up again.

He concluded that the boiler is ok, but there is a hole on the coil pipe in the tank. And because the tank is not covered by the policy, he suggested me to replace the entire system with a new combi boiler.

He seems to be knowledgeable and said he is 100% sure about the problem he identified.

I just hope that someone here can give me a second opinion on what went wrong. I agree with what he said but still have one question - if that is indeed what went wrong, when I turned off the main valve before I left house for a couple days, the pressure should still remain (before kicking the pressure relief valve on) rather than dropping to zero when I came back?

And what options do I have now to fix the problem? Should I replace the tank or perhaps the whole system with a combi boiler?

Any suggestions would be greatly appreciated!

Thanks,
Deisler
 
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I would also want to test if any mixer taps were letting by, ie: mains cold water seeping back into HW system.
 
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I would also want to test if any mixer taps were letting by, ie: mains cold water seeping back into HW system.

Hi I just found one of the shower mixer (which we have not used for at least 6 months) have condensation all over it and it feels very cold.

There is a buzzing sound coming from the mixer, and from the pipes behind the tiles. See here http://imgur.com/oNKkFfp

Could this be the problem that is causing the high pressure in the boiler?

I get the idea of cold water seeping into the cylinder through mixer tap, but how can this increase the pressure in the boiler (which is connected to the CH directly I suppose?)?
 
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the coil inside the hot water cylinder is connected to the radiator circuit and as hot water from the boiler passes through it ( like it passes through radiator ) it heats the water that surrounds it and hey presto it comes out the hot water tap, hot. if the coil is ruptured the cold water around it ,at mains pressure ,will go in and increase the pressure in the central heating /boiler. you told us that you turned mains off when you went away and when you got back pressure was zero, but you also told us there is a leak under the boiler,over a few days you lose the pressure there. hope this helps.terry
 
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