Central Heating Woes

[Coldtoes]

I was very grateful for your advice just over a month ago. My story as briefly as I can is...

Our radiators downstairs have been totally cold most of the winter. We put in the necessary chemicals in the system and flushed it through, several times. Then took all the radiators off the walls and flushed out large quantities of dark sooty looking sludge, like melted choclate, out of each radiator. We have since added inhibitor.

Meantime there are the most disturbing noises eminating from the boiler / hot water cylinder which sound at worst like bombs going off inside the system, at best like pops and cracks which rocket up and pump water over into the feed and expansion cistern. We havent replaced the pump as it still appears to be working and does not sound like it has failed, in that it is still making whirring noises....

A boiler person that came round diagnosed a blockage in the system and said we would need a power flush. We have since cleaned out all the radiators and flushed the system manually - surely that would have dislodged any blockage? What else can be causing the noises and radiator failure...We are extremely skint at the moment and if possible want to sort out this problem ourselves - what should we try next?

Again your advice will be most gratefully received!

Coldtoes (still!)

[Roger Mills]

Did you flush the pipes out while doing the radiators? If so, how?

[ronnie]

Sludge by its nature tends to accumulate in the lower section of the CH system. If you have removed large quantities of sludge from the radiators it follows that there will be similar deposits in the pipes supplying the radiators. The symptoms would point to a failure of the system to circulate. You should identify the lowest pipes in the system, disconnect them and back flush with water. As you have introduced an inhibitor, it would make sense to collect this when you drain the system. This is an exercise in logic. Go for the lowest, most accessable points and progress though the system. Best of luck

[Michael Chare]

It is possible to hire power flush equipment. Though using it is not a simple job!

[Coldtoes]

Thankyou for your helpful responses. Please forgive my followup questions - they will probably sound really stupid to those who have a plumbing background - however I am learning by doing, and learning fast!!! So here goes....

1) When we flushed through the system (weve done this about 4 or 5 times now) the water now runs clear. Where would the blockage be occuring if it appears that water is running through the system?

2) Why is it that a blockage causes the other symptoms of banging and crashing in the system? Im afraid that something has gone wrong inside the hot water cylinder or between the boiler and the cylinder. The cylinder also seems to get very hot - probably overheating.

3) Do you have any instructions as to how to 'back flush' the pipes. Would I have to connect a hose pipe and flush through mains water?

4) How would I collect the water with inhibitor in it?

5) Would there be any point in changing the pump even though it sounds like its working?

6) Should we just bow our heads to the inevitable and pay out for the powerflush as first advised?

Again, all advice very gratefully received.

Coldtoes.

[Owain]

There are multiple parallel paths for the water to flow in most radiator systems.

When water gets hot it boils, or releases dissolved air. If the heat from the boiler cannot be dissipated from the rads, the cylinder will get very hot.

You may also have airlocks in the system from the draining-down, which actually sounds more likely to me than an actual blockage especially now you have clean free-running water. These can often be cured by filling the system slowly from the bottom by a hose attached to the drain valve, rather than from the top via the tank.

Is basically it, with precautions to avoid contaminating the mains supply or pushing too much water in and flooding the loft.

Bucket under the drain valve at the lowest point.

If you're sure it's working, why change it.

I wouldn't pay for a powerflush unless you know the problem is physical blockage.

Owain

[gasman pete]

can i just enquire a couple of things!!!!! is it on a gravity hot water system or pumped? if it is the former there might be a anti gravity valve on the vertical flow pipe from the boiler.if it is the later is there any heat in the rads at all ? peter