Central heating blockage?

bcutts · 19 Jan 2003

Having HUGE problems with my central heating.

Yesterday I wanted to flush the system and add corrosion inhibitor. I opened the drain cock at the bottom of the system and it drained away quite happlily whilst filling the header tank in the loft from the cold water supply. I then added the contents of the inhibitor an allowed it to be drawn into the system.

After a couple of minutes, the flow from the drain cock stopped and the system now refuses to fill from the header tank.

Could something have been drawn into the system and caused a blockage. If so, where is this likely to be?

I've tried reverse flushing the system from a hose connected to the drain cock but all that happen is that afer a while, the water flows out of the system expansion pipe into the header tank.

Somebody please help as my wife is getting cold & angry

!!

Brian

breezer · 19 Jan 2003

I am not a plumber or heating engineer, but as you say id does seem probable you have a blockage.

Could you not "connect" the hose to the "input" from the header tank and Tempoary block the expansion pipe, if it wont go one way perhaps it will go the other

simon · 19 Jan 2003

have you opened any/all bleed valves on the rads and the system bleed normally at the highest point but may be by the cylinder?

bcutts · 19 Jan 2003

I've tried opening several bleed valve on upstairs and downstairs radiators at the same time. I also opened the valve on the pump to get it to fill with water so that I could perhaps run the system and clear the blockage but to no avail.

I'll try connecting a hose to the inlet for the system and try flushing the other way.

Will it harm the system if I plug the expansion overflow when I try flushing again?

Regards,

Brian

simon · 19 Jan 2003

I'm not sure exactly what you've done.You tied off the central heating tank (the small one) in the loft right?,then drained down the radiators through the lowest drain off cock so there's only an inch of water in the small tank.Then you closed off the drain off and opened a bleed valve on a rad went back in the loft untied the ballcock and mixed your fernox (or whatever) with the water as the tank filled?
I presume this is the way it went if not can u explain how you did it.Also are you sure you opened the system bleed a short vertical pipe with a small screw cap on it?,if u undid this and no water or air came out get a small nail or similar and gently release the blockage or make sure the rubber seal is not sticking blocking the hole.

simon · 19 Jan 2003

By the way it won't hurt to block the vent pipe just to flush the system

bcutts · 19 Jan 2003

Simon,

Yes I did pretty much as you suspected - other than the fact that the fill for the expansion tank has a stop-valve so I didn't havce to tie up the ball-cock.

I blocked off the expansion vent pipe and tried reverse flushing with all the radiators closed and after a few minutes, the water started to fill the expansion tank. The system now seems to fill from the expansion tank and I've bled the pump and the radiators and got the system running.

I can't find the vent pipe valve you mentioned. As the system is still somewhat noisy - lots of water gurgling, I may need to bleed that as well - where in the system would I find it - near the pump output?

simon · 20 Jan 2003

Glad you're sorted.As it's in you're own house I'd bleed all the rads tomorrow night and then again next week.
Technically the system bleed valve should be on the highest point of the system ie by your cold water storage tank in the loft somewhere but they're often by the hot water cylinder.

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Central heating blockage?

breezer

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