Feed and Expansion Tank Overflowing

[owensben]

Hello,

My wife and I and trying to find the cause of the feed and expansion tank overflowing.

First of all, here's a brief description of what kind of system we have. Boiler downstairs in the kitchen, hot water tank with immersion in the airing cupboard, a large cold water tank in the loft and a F&E tank next to the cold water tank.

Here's what's happened to date. During last summer (when the boiler isn't on that much) we noticed the F&E overflow pipe was dripping onto our garden patio. On investigation, the water level in the F&E tank was near the top, despite no water being leaking into the tank from the ballcock feed. Both the ballcock and valves in both tanks were replaced by a plumber anyway and some water was removed manually from the F&E tank. We thought it had been fixed but the dripping started a couple of days afterwards.

During the summer months the dripping from the overflow pipe is far more frequent and steady.

There appear to be three pipes attached to the F&E tank. One at the bottom of the tank leading to the airing cupboard/hot water tank, one from the ballcock/valve cold feed and one hanging over the top of the tank which I've never seen anything coming out of before.

As I can never see the ballcock feed leaking when the water is dripping on to the patio, I'm guessing the pipe from the hot water tank is pushing water back up the pipe and into the F&E tank? Having said that, we have checked the temperature of the water in the F&E tank and, although it's not as cold as the water in the cold water tank, it never feels warm.

Can anyone advise from this what might be wrong? Any troubleshooting tips or even fixes would be appreciated!


Ben[/b]

 

[seco services]

a large cold water tank in the loft and a F&E tank next to the cold water tank.

There appear to be three pipes attached to the F&E tank. One at the bottom of the tank leading to the airing cupboard/hot water tank, one from the ballcock/valve cold feed and one hanging over the top of the tank which I've never seen anything coming out of before.

what tank is it ?
you say the f/e tank
then you say it's the tank with the pipe in the bottom going to the hw cylinder feed if so thats the cws tank not f/e.

so what tank is it ?
is it the small or large tank ?

 

[owensben]

Sorry for the confusion.

The tank in the loft which is overflowing is the small f/e tank. It has a pipe attached to the bottom of the f/e tank which seems to go to the airing cupboard. I just followed the pipe and it appears to attach to a red grundfos device. Was it that?

Does that make any sense or am I confusing you more?

 

[seco services]

I just followed the pipe and it appears to attach to a red grundfos device.

that will be the feed pipe for the system
the red grundfos is a pump.
the pipe should tee in just before the pump.

if the f/e tank is back filling from the pipe in the bottom of the tank
then it sounds like the cylinder coil is pin holed.

i take it the other tank (cws) water level is higher than the f/e tank ?

if you find the pipe from the cws to the base of the hw cylinder
half way down in the airing cupboard should be a red gate valve
if you can close that you'll probably find the f/e tank will stop overflowing.

gate valve.

 

[owensben]

Can we close of this valve as a permanent solution? I suspect not?

Does this just help troubleshoot the cause?

 

[seco services]

Can we close of this valve as a permanent solution? I suspect not?

no as this stops the cylinder from filling and you'll get no hw.

Does this just help troubleshoot the cause?

yep.

thats providing the gate valve closes and seals fully.

 

[owensben]

We've shut off the valve from the CWS to the Hot Water Cylinder.

I've emptied out a small amount of water from the f/e tank so it's just below the pipe and stops dripping.

Can you clarify how this will help the f/e tank from overflowing? Will the f/e tank keep overflowing until the water in the Hot Water Cylinder drops below the pin hole?

 

[seco services]

Can you clarify how this will help the f/e tank from overflowing? Will the f/e tank keep overflowing until the water in the Hot Water Cylinder drops below the pin hole?

if the cylinder coil is pin holed it will pass water from the cws to the f/e tank under gravity because the cws is higher than the f/e.

by shutting the gate valve you stop the cws filling the cylinder so the
water can't then pass to the f/e.
but this is only for testing to see if it stops.

otherwise leaving gate valve closed you will have no hot water to any taps
and also you can't lower the water level to below the pin hole as still you will have no hot water.

only solution is a new cylinder.

 

[owensben]

I thought that might be the answer.

Well we left that gate valve shut off for around 30 minutes and the f/e tank level didn't rise. I have turned the gate valve back on and the f/e tank is starting to rise again....So guess new cylinder.

Thank for your help.

Couple of quick questions though?...
If this has been the case for the past year, is that bad for our health?
Why wouldn't the dripping be happening in the winter when the boiler is in use more?

 

[seco services]

Couple of quick questions though?...
If this has been the case for the past year, is that bad for our health?

no thats why you have the cws higher than the f/e so clean water passes to the f/e not f/e water passing to your bath water.

Why wouldn't the dripping be happening in the winter when the boiler is in use more?

useally it will happen all the time the pin hole won't know what time of yr it is.