Black Water

[baluachrach]

Hi I have just turned back on my central heating after being off for 5 months. I went to bleed some of the rads and there was really black water comming out. Would i be better to take the rads off and try to flush out with a hose? or go for a power flush? thanks

 

[JohnD]

cleaning them yourself will save you several hundred ££s on a powerflush. You do not mention blockage or cold radiators so I presume you still have a circulating system.

The question is, which have you got spare? a weekend or ££££s?

If you are fond of plumbing, then (after hosing them out in the garden, which is a good way to get sediment out) you can fit a Magnaclean which will cost you about £100 and may you take an hour or so (assuming you are already drained). it will catch all the loose black sediment that remains in circulation.

You can loosen sediment by adding Sentinel X400 to the circulating water for a few weeks

Remember to add an inhibitor at final fill

Look for any signs of leaking or pumping over which could cause air or fresh water to enter the system and accelerate corrosion.

Bale out and sponge clean the Feed and Expansion ("Header Tank") in the loft to remove the mud and sediment rather than letting it be washed down into the rads when you refill. Fit a lid and insulating jacket to it.

 

[baluachrach]

Thanks for that no leeks but a couple of the radiators dont heat up in the middle. Sorry but what does pumping over mean?
Think I will try flushing them myself this weekend and fitting a magnaclean sounds like a good idea. Can it be installed anywhere in the system?

 

[wiggikins]

Normally on return to boiler, but you get installation instructions with it anyway!

Keith.

 

[JohnD]

The feed and expansion tank (usually) has:

a supply pipe in the side near the top, supplying fresh water through a ball-valve to maintain the level

a feed and expansion pipe in the side near the bottom which tops up the circulating water (and also receives expansion when the system heats up)

a vent bent over the top, which allows any excess pressure or steam to escape if something goes wrong.

Pumping over occurs if, due to a blockage or incorrect piping, water comes out of the vent pipe and gushes into the F&E. If it does this, it picks up dissolved air which causes more and faster corrosion. It "should" never happen.