# Repressurising central heating system



## burger1979 (27 Oct 2008)

Hi,

I was wondering if someone could tell me how to re pressurise/refill a centrl heating system? our water was cut off this morning and then when i to turn the heat on the boiler cut out. i checked the systems pressure and it was less than half a bar. the system needs at least half a bar to start running(according to the manual). anyway i thought it might be air in the system so i let the air out through the air vent. then when i went back to check out the pressure it hadnt changed and the boiler would not ignite. the system is sealed and i dont know how to refill it. i thought that if the system is sealed then the boiler would let in the water when required. anyone any pointers???

thanks
burger.


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## jhegarty (27 Oct 2008)

there should  be a valve to open to fill the system....


could also be airlock of course , did you bleed the radiators ?


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## burger1979 (28 Oct 2008)

yeah i got all the air out of the rads by going around and loosening the air vents on the side till water came out. i will go home later and fiddle around with the valves in the hot press and see if one of them opens up to refill it (never even thought about doing that) thanks for the reply.

burger1979


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## secman (28 Oct 2008)

There is usually a valve in hot press to top up central heating system. We usually only open it for about 5- 10 seconds and then vent the highest rad in house(ours in attic conversion) and air gushes out of it very quickly.

Secman


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## Boyler (28 Oct 2008)

burger1979,
I would be worried if the mains water supply turning off caused a drop in your heating pressure ie. heating water leaking into your mains water. There should be a check valve and a ball valve between the mains supply and your heating circuit (filling loop). In some cases the filling loop is removed so that the heating circuit is separated from the mains.


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## burger1979 (28 Oct 2008)

Boyler,

some one in work suggested this to me today so i will have a look when i get home later on. i think though that there should be a check valve on the line to stop that from happening. but i'll check the valves later in the hot press and see if that can fix it. 

thanks again for the replies
burger1979


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## DavyJones (28 Oct 2008)

burger,

Under your boiler you may see a silver fexlible pipe that loops from one pipe to another. On this fexlible pipe there should be a black handled valve. When the handle on this valve is running with the pipe it is on, when the handle is running  across the pipe it is off (like an X = off.). It is very important that you only have this valve on for short bursts and keep an eye on the clock, stop when needle hits 1 bar.

This silver fexilble pipe may be under boiler or in hot press.


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## burger1979 (29 Oct 2008)

right the problem has been fixed. i found the line that feeds the boiler from the water tank in the attic. There is only one tank in the attic that serves the whole house. The line for the boiler also serves one of the showers in the ensuite in the spare bedroom. We got in a plumber last night to see if he could get it going and he could. he drained the system partially through the pressure relief valve in the boiler itself then flicked it on. it splurged into life and the water pressure gauge worked its way up to just below a bar pressure (it needs a 1/2 bar min to work.) anyway the plumber said that the boiler should have its own dedicated line from the tank rather than being feed off the line feeding the shower (cheap installation by the original builders/plumbers). also the motorised valves thjat control the heating circuits for the house (2no) look like they are getting 'stuck' and this is causing a little air to get into the system. also some of the rads just need to be balanced again as some of them did not heat up after heating was on for a while. so thats about it. 

thanks for all the replies, oh the joys of house ownership


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## DGOBS (2 Nov 2008)

the boiler should NEVER be fed from your domestic tank at all. As this leaves only a single check valve seperating your domestic water from ur system water and they can and do fail. And then ur system water would mix with domestic water!!!!!!!!!!!!
Eittyer have you plumber install a makeup tank to feed your system or better again have him seal your system completely add an expansion vessel if required (if ur boiler is a system it may not be required) and supply u with a filling loop


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## aircobra19 (7 Nov 2008)

DGOBS said:


> the boiler should NEVER be fed from your domestic tank at all. As this leaves only a single check valve seperating your domestic water from ur system water and they can and do fail. And then ur system water would mix with domestic water!!!!!!!!!!!!
> Eittyer have you plumber install a makeup tank to feed your system or better again have him seal your system completely add an expansion vessel if required (if ur boiler is a system it may not be required) and supply u with a filling loop


 
If the system water does get mixed with the domestic water (faulty valve now fixed) is it simply a matter of draining all the hot and cold water, (tank & cylinder) Then refilling them? The Heating system is at correct pressure, and I don't there was ever anything added to the water in the heating system. Though its probably not very clean.


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## DavyJones (7 Nov 2008)

aircobra19 said:


> If the system water does get mixed with the domestic water (faulty valve now fixed) is it simply a matter of draining all the hot and cold water, (tank & cylinder) Then refilling them? The Heating system is at correct pressure, and I don't there was ever anything added to the water in the heating system. Though its probably not very clean.




If you drain everything down and then just flush it through for a few minutes, that should do it.

When you say correct pressure, what is that? Is the heating fed from storage tank with a non return valve fitted on line? Do you have an expansion vessel?

I would fit a filling loop and not run the risk of cross contamination in the furture.


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## aircobra19 (7 Nov 2008)

I emptied the domestic system, tanks, last night. Took the opportunity to clean the sediment from the tanks while they were empty. Half filled it, emptied it, then fully refilled it. I assume since the heating was at the correct pressure the heating circuit was therefore full that the water comming into the tank was mainly from the mains water, (via the filling loop) that had no where else to go. 

Seem like there was no non return valve fitted on the line. Just a regular valve that seems to be suspect. I thought it wasn't working. Originally there was no filling loop so I had one added after. I think because the of the suspect valve which couldn't be opened.  

I wasn't there. But I'm guessing someone opened the filling loop in error, mistaking it for a shower feed. The original plumbing is very messy. Pipes every where at all angles. The regular value from the tank must have been open, or partially open. But I don't undertand why the boiler didn't read too high a pressure if that valve to the tank had been open for a few weeks.


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