Emptying cemtral heating tank

camerart · Posted: Thu Apr 05, 2012 10:30 am

Hi,

I'm moving a radiator, and need to empty the pipework.

I've locked the ballcock up in the small tank (Central heating) this feeds the coil inside the hot water tank, and no valves.

First I closed all of the other radiator valves, then I emptied the pipework at each end of the old radiator. Checked the tank and it's still full. Shouldn't it have emptied?

Cheers, Camerart.

SimonH2 · Posted: Thu Apr 05, 2012 7:15 pm

This really belongs in Plumbing ...

From what you describe I'd expect the F&E (Feed and Expansion) tank to be empty. Did you leave the valve open on the rad you are moving ? If not then you'll have drained the rad but not the pipework.

camerart · Posted: Thu Apr 05, 2012 8:43 pm

Ok, I'll move it to plumbing, thanks.

JohnD · Posted: Thu Apr 05, 2012 9:23 pm

how much water came out of the valves at the ends of the old rad when you opened them after removing the radiator?

camerart · Posted: Thu Apr 05, 2012 9:40 pm

JohnD wrote:

how much water came out of the valves at the ends of the old rad when you opened them after removing the radiator?

About a 1/2 gallon.

JohnD · Posted: Thu Apr 05, 2012 9:55 pm

do the pipes to the rads come down from the ceiling?

when you look in the feed & expansion tank, how deep is the mud in the bottom, and what colour is the water?

do you know when it last had inhibitor or cleaner added?

camerart · Posted: Thu Apr 05, 2012 10:09 pm

JohnD wrote:

do the pipes to the rads come down from the ceiling?

when you look in the feed & expansion tank, how deep is the mud in the bottom, and what colour is the water?

do you know when it last had inhibitor or cleaner added?

The pipes come along the hall ground floor, from boiler ground floor.

The tank had about 3 gallons in it, with a brown covering of sludge about 1" on the bottom. I syphoned it out, then put cleaner in. Then I noticed the outlet is 5inches up, so the chemical is still in there. I have inhibitor for later. I doubt it has had inhibitor in for 30 years, if any. When I drained the water, it was black.

JohnD · Posted: Fri Apr 06, 2012 7:18 am

it is very possible that there is now a blockage in the feed and expansion pipe. Most usually it is where the 15mm joins onto the large circulating pipes. If you hold a magnet against this T-joint, is it attracted? If so it will be the black iron oxide sediment. Unless it is a compression joint that you can undo, you will have to cut out and replace the blocked section.

camerart · Posted: Fri Apr 06, 2012 8:09 am

WOW! I bet you are correct. When I was syphoning the tank, the syphon kept blocking. There's a compression joint handy, on the silver downpipe, which might give you an idea of it's age. I predict a soaking in dirty water this morning.

Thanks JohnD, I would have never guessed.

45yearsagasman · Posted: Fri Apr 06, 2012 8:54 am

If it has blocked in this area, block off the cold feed outlet in the exp tank before you start cutting the cold feed, and have some towels to hand.

camerart · Posted: Fri Apr 06, 2012 9:10 am

45yearsagasman wrote:

If it has blocked in this area, block off the cold feed outlet in the exp tank before you start cutting the cold feed, and have some towels to hand.

OK. I just did JohnD's check with a magnet, and it's not magnetic till I get to the 28mm, which I think must be steel pipe, as it's magnetic all along. I'm just off to attack it.

Thanks.

camerart · Posted: Fri Apr 06, 2012 3:36 pm

First I scooped the chemical cleaner out out the expansion tank. Then tried to loosen one side of the compression fitting at 15mm to 28. It moved a little, then I realised I wasn't going to be able to tighten it as there is no room.

The outlet of the Expansion tank is 4 inches up, and there is a little extra thread poking out from the seal, so I soldered a length of 15mm to a fitting, screwed it onto the outlet, and made a little pump. Violent pumping and the blockage cleared. Then I added some garden hose to syphon it from the bucket.

All working, again with a new rad in the kitchen.

JohnD's prediction that there might be a leak was correct, and my prediction that I will get soaked was also correct, so happy days.

Thanks all, Camerart.

JohnD · Posted: Fri Apr 06, 2012 3:47 pm

time to use your cleaning chemical soon!

I like your pump idea.

camerart · Posted: Fri Apr 06, 2012 4:56 pm

JohnD wrote:

time to use your cleaning chemical soon!

I like your pump idea.

I left it in the tank 'for next time!'

I didn't explain well. I scooped the chemical into a bucket, pumped the blockage clear, then attached a hose to the pump pipe and syphoned the chemical into the system.

It could have been diluted though with all the messing about, will it still work?

In hindsight, I think I should have finished the job, then emptied the water out of the Kitchen radiator, and poured the chemical into one of the top plugs.

camerart · Posted: Fri Apr 06, 2012 4:57 pm

JohnD wrote:

time to use your cleaning chemical soon!

I like your pump idea.

I left it in the tank 'for next time!'

I didn't explain well. I scooped the chemical into a bucket, pumped the blockage clear, then attached a hose to the pump pipe and syphoned the chemical into the system.

It could have been diluted though with all the messing about, will it still work?

In hindsight, I think I should have finished the job, then emptied the water out of the Kitchen radiator, and poured the chemical into one of the top plugs.

Thanks for your help.