Central heating blockage, airlock or something else?

Joined
31 Oct 2009
Messages
14
Reaction score
0
Location
Cheshire
Country
United Kingdom
Further to a previous post - http://www.diynot.com/forums/viewtopic.php?t=198419 - I decided to see if a dose of Fernox F3 Superconcentrate Central Heating Cleaner would help me with my lukewarm hot water.

I squirted it into the radiator in the bathroom - losing a bit of water in the process as the injector didn't fit snugly. However, since then I've had no hot water and the central heating has decided to pack up. I assumed maybe this was due to large amounts of crud and limescale being released into the water.

There now appears to be a ridiculous amount of air getting into the system. If I switch off the pump (and boiler) I can hear air bubbling through the pipes. It then takes at least a minute to bleed the bathroom radiator and one of the bedroom radiators. Once I switch the pump back on I can hear air bubbling again back into the same radiators. At the same time the f & e tank pumps over - the water coming from the feed tube (rather than the ballcock). I've also noticed a slight suction if I hold my hand up against the expansion pipe. I guess the air is being drawn from there. I then have to bleed the upstairs radiators again, etc, etc.

So today I attempted to flush the whole system. I drained all the water from the the drain cock by the pump. However, I was unable to drain from the drain cock on one of the downstairs radiators as it's so close to the floor I can't get a hosepipe on it. I'll look to manually flush each downstairs radiator.

Anyway, after releasing the ballcock on the f & e tank with the drain cock still open, nothing came out. Aha, I thought, an airlock. So I connected the end of the hose to the cold tap and gave a few blasts through the system. At one point I left it running and saw water jetting out of the overflow in the roof and (after switching off the cold tap and removing the hose) water draining out. Great, all clear! But after releasing the f & e ballcock and leaving it until it stopped filling I found nothing came out of the drain cock.

How can water go up but not come down? And why am I getting massive amounts of air into the upstairs radiators? Nothing has changed with the upstairs radiators or the hot water. The only radiator which now heats up is the kitchen radiator, which I think is the first one in the circuit.
 
Sponsored Links
Joined
26 Oct 2007
Messages
4,900
Reaction score
426
Location
Kent
Country
United Kingdom
You need to turn the boiler and pump off before you do serious damage by running it dry.
Your problem is almost certainly a blocked cold feed, where it joins the system, near the pump is a good place to look first.
 

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.


Are you a trade or supplier? You can create your listing free at DIYnot Local

 
Sponsored Links
Top