Cold Water Flowing into Loft Central Heating F and E Tank


Postby davekc64 » Thu Apr 23, 2015 3:31 pm

Hi, no doubt this question has been asked before, but I find myself perplexed.

Our CH/HW set up is:
1.Boiler (old but still perfectly functioning) located in kitchen on ground floor.
2. HW cylinder located in airing cupboard on first floor.
3. Cold water storage and CH F&E tanks located in loft, side by side on plinth above the HW cylinder.

A few months back the pump was replaced, burnt out due to the pipe being clogged with gunk and over pumping. Since then the system has been power flushed to clear it out.
This has cleared the system and the over pumping has ceased, no more scalding water going into the F&E tank.
However, before the system was flushed, cold water was flowing into the F&E tank and overflowing. This has continued, requiring frequent bailouts, and this only occurs when the boiler is not running and the system is cold.

In short:
1.The system is not over pumping, the water flowing into the tank is cold not hot, no water is entering via the vent pipe.
2.The float valve has been replaced with a new one, and the level set so that the tank will hold around 6" of water. This is fed from an outlet pipe from the cold water storage tank.
3.All rads have been bled.
And yet cold water is still flowing into the tank, researching this I think that I may be faced with a pinhole in the HW cylinder coil, yet there does not appear to be any cross contamination between the CH water and the domestic HW.

Any ideas or clarification will be gratefully received, as I am totally stumped.
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Postby proptech » Thu Apr 23, 2015 6:41 pm

Hi davekc64

Providing that you can be 100% sure that water is not entering via the ball valve, then the only place it can come from is the cylinder.
But firstly 6 inches of water in the tank seems a bit high. Remember that water will expand when heated, and raise the level. So, lower the level a bit, turn off the inlet to the ball valve, or tie it up, and turn off the boiler Then keep an eye on it for a while. If the level still increases, then it has to be the cylinder. It does happen, but it's not that common.
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Postby davekc64 » Fri Apr 24, 2015 8:33 am

proptech wrote:Hi davekc64

Providing that you can be 100% sure that water is not entering via the ball valve, then the only place it can come from is the cylinder.
But firstly 6 inches of water in the tank seems a bit high. Remember that water will expand when heated, and raise the level. So, lower the level a bit, turn off the inlet to the ball valve, or tie it up, and turn off the boiler Then keep an eye on it for a while. If the level still increases, then it has to be the cylinder. It does happen, but it's not that common.


Thanks for the reply.

Def not the ball valve, and this morning another 7L of water had to be bailed out before water level reached the overflow.

Oh well looks as if it's a replacement cylinder then.
davekc64
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Joined: Thu Apr 23, 2015 3:01 pm

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