Dripping overflow from expansion tank

[BENSONDOG]

Hi,

I wonder if anyone to point me in the right direction on this.

My overflow pipe from my expansion tank in the loft sometimes drips. It’s a bit of a strange issue and it is very infrequent.

I’ve checked the expansion tank and the water is at least two inches below the outlet pipe. I’ve removed sludge at the bottom of the tank, but still intermittently get dripping.

The water in the tank is fairly warm and may produce condensation. I removed the cover which was a bit wet on the underneath, possibly due to the condensation, and covered half of the tank with a wooden shelf. The shelf is now wet and I’ve had a few drips over the weekend.

Do you think that the dripping is caused by condensation as the weekend was very cold? Warm water in tank/cold air coming back up the pipe = water.

I know that this sounds a bit bizarre, and my wife doesn’t believe me, but I can’t find any other reason.

Any suggestions would be appreciated.

 

[masona]

Do you think that the dripping is caused by condensation as the weekend was very cold? Warm water in tank/cold air coming back up the pipe = water.

Yes, mine does it time to time.

 

[bathjobby]

You have too much water in this tank, should be just enough to cover the pipe at the bottom of the tank that feeds the CH system. Because this is an open vented system the level of the water in the tank is also the level of the water in the expansion pipe, therefore the higher that level, the less expansion is needed before you get over pumping into the expansion tank making the water warm, then on cold days it condesses into the colder overflow pipe giving intermittent dripping.
Lower the level of the water to just above the feed pipe at the bottom of the tank.
Also, how high above the top of the tank does the expansion pipe go before bending back down towards the tank ? It needs to be a minimum of around 18" (50cm) above the top of the tank. Again, the higher this pipe goes means that more expansion is required before overpumping takes place. Lower the water level and adjust the ball valve first, if you still have the problem and your expansion pipe height is less than 18" above the top of the tank height, increase it so that its at least 2.5 feet (80cm) or so.

 

[jonnyb1]

probably the coil in the cylinder is leaking ie domestic and ch mixing.... if this is so change cylinder check by tieing up the ballvalve for a day or two

 

[kevplumb]

if the coil was leaking it would be constant

 

[bathjobby]

Agreed Kev, bet hey, lets not lower the water level that we know is too high, let change the cylinder instead, lol. Sorry, couldn't resist.

 

[kevplumb]

feel free we all do it

 

[jonnyb1]

in reply to the problem not being the coil in the cylinder...the water level would drop in the expansion tank when the hot water is being drawn off.theory of relativity if it goes up it comes down

 

[kevplumb]

scuse me in advance BO**OCKS

if its pinholed it dont happen