[Help] High pressure in boiler and leaking from overflow pipe - pinholed coil?

Deisler

Hi All,

Just trying my luck here to see if someone can help me identify issue with my boiler/hot water tank.

I have a boiler (Mynute 28e) and a hot water tank (Flamco 210L) , 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. Then I checked the boiler and the water pressure shown there was very high (~3bar). Apart from that, everything worked fine (CH and HW wise).

I had a plumber who checked the system for me earlier:

1) He opened the boiler and turned on a valve inside to release the water from the system out through the overflow pipe, and the pressure went down, but then climbed back up slowly again.

2) He went to the hot water tank, and checked the filling loop (which was properly closed).

3) He then turned off cold water feed to the tank. After releasing the pressure, the pressure still slowly climbed back up.

He concluded that the boiler is ok, but the coil in the hot water tank is pinholed. 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. Are there any other reasons that could cause this?

Apparently replacing the tank or with a combi boiler could be very costly so I want to make sure the tank is faulty before spending the money.

Any suggestions would be greatly appreciated!

Thanks,
Deisler

Alex1983

Definitely possible. How quick does it rise? If it is with a couple of hours you can turn the water off to the tank for the day and if the pressure doesn't rise then it will definitely be the tank.

Check with the tank manufacturers as a lot of tanks have 20-25 year warranty.

Deisler

Alex1983 wrote: »

Definitely possible. How quick does it rise?

When the cold water feed to the tank is turned off , it rises from 0 pressure (after releasing the pressure from the valve on the boiler) to green zone in 10-20 seconds, then up much more slowly to 2.5-3 bar.

Alex1983 wrote: »

If it is with a couple of hours you can turn the water off to the tank for the day and if the pressure doesn't rise then it will definitely be the tank.

If the water feed is off to the tank, then the pressure should increase if there is a split coil rather than staying low? Or perhaps I misunderstand something?


Yes, thanks for the advice - just checked with the manufacturer - it only had 3 year warranty .


D

Alex1983

Disconnect the filling loop and turn the water off to the cyclinder, release the pressure to zero and leave it for a while with heating and hot water off. Nothing should happen it should stay at zero.

If nothing happens in a couple off hours turn the water back on to your tank and leave that another couple of hours, the pressure should still stay at zero. If it rises then I would think it is the coil in the tank.

Deisler

Alex1983 wrote: »

Disconnect the filling loop and turn the water off to the cyclinder, release the pressure to zero and leave it for a while with heating and hot water off. Nothing should happen it should stay at zero.

I did exactly what you suggested: Filling tube disconnected, cold water feed to the cylinder turned off. Release the pressure from the boiler to zero.

Then the pressure went back to 1.2 bar within 10 seconds after I stopped releasing it, and has been gradually climbing up since then (now almost 2 bar, after 10 mins).

Seems strange to me... Is this definitely a sign of internal leaking from the coil in the cylinder?

Alex1983

Unfortunately I think it probably is. It can be proved by draining the heating system and disconnecting the coil and see if water comes out.

Alex1983

You have cold water getting into your heating system and the only place cold water pipes touch heating pipe/system Is the filling loop, which you've disconnected and the coil.

Deisler

Alex1983 wrote: »

You have cold water getting into your heating system and the only place cold water pipes touch heating pipe/system Is the filling loop, which you've disconnected and the coil.

Thank you for your reply.

I just did one more test:

Turn off the cold water feed into the cylinder. Filling loop off. Drained the entire cylinder, with the gate valve (the one into the house) turned off. I assumed this means there is absolutely no water in my house. Waited for 5-10 mins, the pressure gauge on the boiler stayed at zero.

Then I turned off the drainage of the cylinder (so it can refill), but kept the feed off (so no water can get in).

As soon as I turned on the gate valve, the pressure slowly climbed up.

Surely this is a sign of leaky coil?

Alex1983

Yes, don't think you got any option but a new unvented cyclinder

Deisler

Alex1983 wrote: »

Yes, don't think you got any option but a new unvented cyclinder

Oh well.... I just found something strange...

We have a bedroom with a shower in its en-suite, and they have not been used for months. I found a lot of condensation over the entire shower mixer and it feels very cold at both ends (like temperature from the mains). We have the same mixer in another room (which we use daily) and it has no condensation at all.

And I can hear a buzzing sound (very low but I can definitely hear it) from the mixer, even when it is completely shut off (i.e. no water coming out). I can also hear a slightly louder sound from the back of the tiles where the mixer is connected to. The shower room is at the corner of the house so the pipes behind the tiles should only be for the shower.

I tried all the other mixers in the house, and no noise at all.

Could this mean that the mixer is letting by, so the cold water can gets into the hot water tank through there, thus the high pressure in the system?

Thanks,
D

Deisler

Here is a pic of the mixer.

http://imgur.com/oNKkFfp

Not sure if it is very clear but it has condensation all over it, and feels very cold. Buzzing sound from it and from behind the tiles.