repair drip from heating expansion tank?

[mfripp]

We recently moved into a new flat and discovered that the copper expansion tank for the heating system has a slow, steady drip (one drip every few seconds). The drips seem to occur whether or not the system is running. The tank is surrounded by styrofoam insulation and a steel casing, so it is hard to tell exactly where the drips are coming from.

The heating system is probably about 15 years old. It's possible that the tank has been dripping for some time without being noticed, because it is in a dark corner of a closet, near the hot water storage tank, and it may usually be warm enough to evaporate all the drips.

I looked inside the tank, and the water level seems to be about 3 inches above the outlet pipe and about 2 inches below the overflow pipe, which makes me think the ballcock valve is working correctly.

Does this mean we will need to replace the tank? Any advice on where we would buy a new one or how much they usually cost? The current one is from Harton Heating Appliances in Kent. We are in Oxford.

 

[compheat]

The chances are its leaking from a connection that goes to the tank rather than the tank itself. you need to have a good look before making decission thats could cost you hundreds of ££.

 

[SuperMario80]

Are you 100% sure it's a leak? Could it be condensation?

 

[Burnerman]

I think he's talking about an Elsan system?
John

 

[ManxPlumber]

Is the water dripping off the underside of the lid as a result of evaporation/condensation

 

[mfripp]

Hi everyone. Thanks for all your responses.

Is the water dripping off the underside of the lid as a result of evaporation/condensation

No, there is no sign of condensation. The air and tank are fairly warm, usually around 25°C, since they are in a small closet with the main hot water storage tank.

I think he's talking about an Elsan system?

I'm not sure what an Elsan system is. This system has a large cold water storage tank (500 liters?), and below that is an insulated hot water storage tank (100 liters?). Then there is the leaking expansion tank (I assume it's an expansion tank) up near the ceiling (about 6 liters). This tank has an inlet from the cold water mains with a ballcock valve, an overflow drainpipe, and two copper pipes plumbed into the boiler/hot water storage tank system. One of the copper pipes is plumbed into the bottom of the expansion tank (its connection could be the source of the leak, it's hard to tell), and one spills into it from the top (the pipe just points down through the lid, with no direct connection). Then there is a pressure pump and various copper pipes leading to the boiler, radiators, taps, etc. I've attached a photo of the tank, highlighting the corner where water is dripping from (you can ignore the strange white cord dropping down from it; that was just my attempt to guide the drips into a container).

radiator expansion tank

• mfripp
• 10 Jan 2010
• 2

Are you 100% sure it's a leak? Could it be condensation?

I don't see any sign of condensation anywhere in the closet, and the drips seem to continue even if the system is left off for several weeks at a time. So I don't think it's condensation.

The chances are its leaking from a connection that goes to the tank rather than the tank itself.

Thanks for this idea -- I'll try tightening up the lower connection. Is it more common for connections to work loose than for the tank itself to spring a leak?

 

[Burnerman]

Just a tip mate but why not leave it until such a time when you can afford to have a drain down - i.e when the weather improves?
I doubt that just tightening things will do it, and there's a good chance of making it worse.
Up to you though!
John

 

[mfripp]

Thanks for the advice everyone!

Just a tip mate but why not leave it until such a time when you can afford to have a drain down - i.e when the weather improves?

I think this is the advice we'll take for now. As we just bought the flat, we were hoping we could get the former owners to pay for the repair, so we thought we should do it right away and get the process moving along. But they are not so keen on that idea, so I think we'll just leave it for now. I've put a "drip tray" under the tank, and water seems to be evaporating as fast as it collects now, so the situation is stable.

We may convince ourself to put in a combi boiler and remove the nuclear submarine hardware by the time spring comes!

It turns out we may have a more urgent leak under the bathtub anyway! (photo attached). If there's lots of corrosion on a copper pipe joint, is that usually evidence that it's leaking? (Other sources could be condensation on the cold pipe or bad sealing around the side of the tub.)

tub hot water elbow corrosion

• mfripp
• 26 Jan 2010
• 1

 

[Nige F]

I think he's talking about an Elsan system?
John

Chemical toilet or elsOn..... as to the bath. It might be just a new fibre washer needed on the tap connector that`s out of shot @ the top of the pic.. That looks like surface corrosion , and it`ll clean off . Worst case renew that bit of pipe with a flexi connector. Should be a 1 hour job and a few parts ...for any plumber

 

[Burnerman]

Elsan.....
Agreed, there seems to be a trail thats run down from above the pic shot somewhere.
John

 

[mfripp]

That looks like surface corrosion

I finally got a chance to dig deeper, and yes indeed, the faucet was not properly tightened down to the tub, so water was getting under it and running down the hot pipe. The locknut on the bottom of the faucet wasn't even finger-tight on the hot side. I tightened it up, and that seems to have taken care of that part of the problem. Good thing the cold side is already tight, because there's no room to swing a wrench between the wall and tub on that side!

Now I just have to re-seal the tub to the tiles. It turns out that is the biggest leak of all in this house (so far!). Water has been running down the side walls under the tub and creating a pool that seeps invisibly under the adjacent walls, eating away at plasterboard and trim in the living room and kitchen. Better fix that before we put in the laminate floors! Now my only concern is how we will find out when the new caulk pulls away ten years from now. (It was pure coincidence that I found these problems, while figuring out the plumbing for a clothes washer installation.)