Hot Water in CH Header Tank

kimgas · 26 Nov 2004

I am have a problem with Hot water in my Ch header tank in the loft, this is obviously coming from the vent pipe to the tank , but Why??
I have turned down the pump and turned down the tank stat to try to solve the problem. The header tank is now full of brown hot slime in the bottom.. is this a diverter valve problem?? comments please

PEDANTICVINDICTIVEMAN · 26 Nov 2004

Has it allways done it or just started recently, new pump been fitted ?, if it's recent it's most likely a blocked cold feed.

brumylad · 26 Nov 2004

Could check the above by using a magnet. The cold feed is the thinner pipe which drops down from the header tank (expansion cistern) to join the heating pipes usually on the first floor and usually near the pump.

If a maget sticks to the copper pipe its full of iron sludge.

Could also be water level in expansion tank too high, water in the expansion pipe will be the same as that in the tank, therefore, if it is high, it will take very little expansion of the water in the pipe for it to flow into the tank.

Is the float controlled valve in the header tank dripping ?

kimgas · 26 Nov 2004

brumylad said:
Could check the above by using a magnet. The cold feed is the thinner pipe which drops down from the header tank (expansion cistern) to join the heating pipes usually on the first floor and usually near the pump.

If a maget sticks to the copper pipe its full of iron sludge.

Could also be water level in expansion tank too high, water in the expansion pipe will be the same as that in the tank, therefore, if it is high, it will take very little expansion of the water in the pipe for it to flow into the tank.

Is the float controlled valve in the header tank dripping ?

I have been in loft and made sure ball cock is OK.. Its not sticking, the small pipe you refer to, I take it you are refering to the cold feed from the tank to the CH system not the rising main feed .. The level in the tank was quite high- about 4" from the top.. I was thinking of shutting down and refilling with a inhibitor, will this help?? also clean header tank out of all gunge etc!!

I will try to alter the float valve to adjust the water level as well

When I was in the loft the HOT water was coming out from the vent pipe with some force and causing the overflow on header tank to run.. any more help would be appretiated..thanks

ChrisR · 26 Nov 2004

4" from the BOTTOM is about right.
Pumping over like that will corrode your system fast. Look at the layout of the pipes - can be hard. There shouldn't be enough pressure difference between the feed and vent pies for pumping over to happen. Do the magnet checks too.
If the water is getting round the heating system OK and it's hard to get to pipes to correct a layout detail, you could try adding a bit of pipe to the vent in the loft to take it high up before it goes down again.
Or, depending on the boiler, you could possibly convert it to a single feed system.

kimgas · 27 Nov 2004

ChrisR said:
4" from the BOTTOM is about right.
Pumping over like that will corrode your system fast. Look at the layout of the pipes - can be hard. There shouldn't be enough pressure difference between the feed and vent pies for pumping over to happen. Do the magnet checks too.
If the water is getting round the heating system OK and it's hard to get to pipes to correct a layout detail, you could try adding a bit of pipe to the vent in the loft to take it high up before it goes down again.
Or, depending on the boiler, you could possibly convert it to a single feed system.

Good info..cheers.. I have drained the system down, cleaned out the header tank and re-filled, put in Fernox (flushing/cleaning agent) I will leave this in for a few days and drain , flush refill..
Qestion is : why does it only overpump now.. I have lived in the house for 10 years without a problem.. thanks for your help..Ah yes it must be cold where you are!!

jonP · 29 Nov 2004

After 10 yrs ! Sounds like it could be a failure of the heating coil in the hot water cylinder. If the cold water header tank water level is above the water level in the ch expansion tank a leaking ch coil would cause hot water to flow into your header tank. Try draining down the hot water cylinder and see if this stops the pumping over. If the tank seems never to drain this would confirm a leaking ch coil which would be filling the tank.

Hope this helps.

kimgas · 29 Nov 2004

Hi

The plot thickens!! It now appears to be the multiport valve. as the problem only happens when the heating and water is selected. if it is on water or heating only all appears OK.. Methods of elimination here I think. I am going to change the valve . Will post my findings here later on. Thanks

smarriott · 12 Dec 2004

Sounds very much like the problem I have; interestingly enough two weeks after hot water started venting into my CH header tank the multiport valve stopped switching and I had no central heating. Having opened the value manually the heating came back on.

I suspect this may explain the venting, although I have not replaced the valve, or the actuator [it's a Honeywell 2-port that has a hot-swappable actuator].

Have you replaced the value/actuator and did this fix the problem?

Cheers

daveyr · 19 Dec 2004

Kimgas

did you get this sorted...I have a similar problem !!

ChrisR · 19 Dec 2004

Start a new thread - all situations are different.

mike1000 · 10 Jan 2010

kimgas said:
I am have a problem with Hot water in my Ch header tank in the loft, this is obviously coming from the vent pipe to the tank , but Why??
I have turned down the pump and turned down the tank stat to try to solve the problem. The header tank is now full of brown hot slime in the bottom.. is this a diverter valve problem?? comments please

Tte open vent and cold feed should be connected before the pump ,no more than 150mm apart ,the sludge in the system would suggest that pumping over has been happening for some time.A quick fix to get you out of trouble would be to fix a plastic bag over the end of the cold feed with an elastic band ,you should find the tank will then be cold.ps adding chemicals aint going to sort it.

JohnD · 10 Jan 2010

kimgas said:
Posted: Fri Nov 26, 2004 7:07 pm

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Hot Water in CH Header Tank

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