Flushing expansion tank outlet pipe

[mojouk]

Hi,

A few of my radiators have been playing up over the winter, and have been a combination of completely cold, and cold/warm at the bottom. The other 2 are/were fine (really hot). Anyway I took 3 of them off at the weekend and flushed them out in the garden with a hose. There was a fair amount of black sludge, but not excessive. I refitted the rads and all seemed well...but now the central heating system will not refill and replace the lost water.

My system is old school, and the boiler is a relic. The system is open vented.

I worked my way back and bled the rads - still wouldn't refill.

I checked the expansion tank ball cock and flow to the tank - both are fine and it fills fine (exp tank).

I have checked the valves on the down pipe from the expansion tank to the cylinder - all open.

Last night I drained the system and cut the supply to the expansion tank - hoping the remaining water would be drawn in - just to prove that there is a flow from the exp tank - still no water going in to the system. Now my rads are empty and I have no water in the system.

I think that there may be a build up of gunk in the pipe between the expansion tank and the cylinder, as there is a fair amount of gunk/weird sludge in the bottom of the expansion tank. I tried clearing the outlet pipe with a wire coat hanger, but still no joy.

After all of this...my question is if I link up a hose from my upstairs cold tap and and push any gunk through the pipe in to the system will this be ok (as in not damage anything?). I know that the pressure would be higher than normal for a system, so would be careful. I then planned to whack in some inhibitor, refill the system and then drain it next week. I really dont want to get the system power flushed as I guess it will cost a lot (£275-375?)? Does this sound about right? or is it a bad idea?!?

I need to get this sorted as we dont have an immersion heater, and cold water is starting to grate a bit now!

I am new to all of this and had never taken a rad off until the weekend, so if what I have done or am suggesting to do seems off the mark please shout out!

Thanks in advance

Matt

 

[Fluffster]

Ideally I would say get it powerflushed.

However there are a few things you can do yourself first.
Backfill the system as you mentioned with mains water do not worry about pressure as the system is open vented.
Once the system has filled up do the usual bleed and add some cleaner not inhibitor to the system.
Make sure it gets into the system and does not just sit in the f/e tank.

Turn the heating on and run it for about a week say for one hour a day to clean the pipework then flush out thouroughly.
Refill and add inhibitor.

Make sure you use a cleaner suited to your boiler heat exchanger aluminium/stainless steel.

Good luck
Pete

 

[mojouk]

Thanks for the reply Pete.

I actually have a blockage in the feeder pipe coming from the expansion tank I think, so I wont be able to get any cleaner in to the system through the f/e tank, but thanks for the advice regarding the back fill.

What I am going to try is getting a hose up in to the loft and blasting down the f/e feed pipe to try and clear any crud that may be there - my main concern is whether this is safe to try? could it damage the pipe work?

After I get it moving (somehow!) I will take your advice and get the cleaner run sorted, and then inhibitor in there at a later date.

Cheers

Matt

 

[Fluffster]

Matt if you have a blockage in the feed pipe it is usually where the cold feed meets the heating 22mm circuit.
Get a magnet and see if it sticks to the pipework in that location.
If so cut it out and replace I doubt you will move a blockage with a hosepipe even a powerflush has problems shifting total blockages.

Pete

 

[mojouk]

Thanks again.

I will try the magnet trick, and pray that all is well!

If it is totally blocked as you say it may be then I think its time to get a plumber in unfortunately, as I'm not sure I'm up to cutting and replacing pipework.

Cheers

Matt