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https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl DIY Forum >> Plumbing Questions >> Hot Water Problem https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl?num=1099696468 Message started by Windy Miller on Nov 5^th, 2004, 11:14pm

Title: Hot Water Problem
Post by Windy Miller on Nov 5^th, 2004, 11:14pm

My Dad has got an old but fairly reliable central heating boiler, but the rads are getting a bit ropey now, so everytime one springs a leak, I bung in a new one for him. The rad change is never a problem, but everytime I have to drain the system down, the hot water system packs up.

Initially I thought the heat exchanger coil thing in the hot water tank was airlocked, so I cracked open the top connection to bleed the air out and sure enough it worked again. This approach worked OK a few times.

Now things seem to be getting worse. Last time I changed a rad, all the bleeding on the world wouldn't fix it, so I had to try another approach. I put a ball valve tee in the expansion pipe in the loft to allow the 'expanded' water to pour back into the header tank. The idea was that the water would circulate and purge the trapped air from the system. Anyhow when this didnt work I was advised by the bloke who fitted the system donkeys years ago that the problem was caused by a buildup of sludge. I put a bottle of that Sentinel 400 stuff in it and hey presto it was OK again about 24 hours later.

Anyhow, yesterday I replaced a seized rad valve, and the hot water packed up AGAIN. Bummer! I put the Sentinel 400 in again, and opened the ball valve on the expansion pipe to get the stuff circulating round the system. The water (?) that came out was certainly dirty but I dont know if that was enough to block anything up.

I dont yet know if the problem is sorted - I am expecting a 'phone call in the morning.

Question is, what is going on here, and if it IS sludge, how can I get rid of it for good? If it's not sludge what's happening? Is it an airlock? ???

Any advice would be much appreciated, as it's starting to p1ss me off!

Windy

Title: Re: Hot Water Problem
Post by HandyMac on Nov 5^th, 2004, 11:26pm

A lot of the sludge can be cleared by connecting a hose pipe to a drain cock and opening it, then pumping the CH system. This should draw in fresh water from the header tank (assuming it's a vented non-pressurised system, don't try it with one of those!).

Alternatively just drain the whole system down after closing the inlet in the loft header tank so that it can't refill. Once empty, refill and run the system for 24 hours. Then drain and refill again.

Don't forget to put inhibitor in the final fill. That'll keep the sludge at bay.

But doing this will likely cause the old CH radiators to develop leaks quicker. Sounds like you could do with a serious overhaul of that CH system if you don't mind me saying.

Andrew

Title: Re: Hot Water Problem
Post by Windy Miller on Nov 5^th, 2004, 11:31pm

You're right about the overhaul Andrew - its certainly due. I would like to change the whole thing for a new system, but neither myself nor the old boy can afford it at the mo!

Windy

Title: Re: Hot Water Problem
Post by thescruff on Nov 6^th, 2004, 9:13am

playing with things you know little or nothing about can cause big bangs and very expensive insurance claims

the expansion pipe is there for a reason, No-one in their right mind sticks valves or anything else on it.

it should be free to atmosphere with no fittings or branches.

do a drawing and i can suggest a few ideas.

scruff

Title: Re: Hot Water Problem
Post by JerryD on Nov 6^th, 2004, 9:28am

Draining down 'dodgy' systems is always a nightmare, it can often take longer to drain down and refill than the actual job you were there to do!

That's why we use the large Co2 cylinder and freeze the pipes wherever we can.

This week I had to break into a one-pipe system to extend it. Two freeze clips on, within 4 minutes both sections were solid, cut out the middle bit of pipe, valve off each end (for later connection of new rads), fit new section of pipe and all done.

The whole job took about 20 minutes!

It would have taken at least that to drain down!

And as for refilling, well that could have taken hours with all the rads to bleed. That's assuming there are no problems................(see Windy Miller post above!).

I also save the cost on renewing the inhibitor :D

Aaahhhh, technology is a wonderful thing ;D

Title: Re: Hot Water Problem
Post by Windy Miller on Nov 6^th, 2004, 5:52pm

Guys - got some photos of this - how do I stick them in?

Windy

Title: Re: Hot Water Problem
Post by thescruff on Nov 6^th, 2004, 6:18pm

Email me a set tolook at for starters when I get back rom snooker 8)

scruff

Title: Re: Hot Water Problem
Post by Windy Miller on Nov 6^th, 2004, 11:06pm

OK here goes with the pics - not sure how it will come out but I'll have a go!

Scruff - No danger of a big bang! �The expansion pipe is permanently venting to atmosphere - the tee'd off section of pipe is the only bit that is controlled by the ball valve. �

The branch is positioned at a level that will allow the 'expanded' water to flow through the valve when it is opened, but will not interfere with the flow through the 'normal' vent. �The valve is a full flow job, so it should not restrict the flow more than any other compression fitting.

The idea of this was to allow the free circulation of water though the system and hopefully to purge any trapped air in the heat exchanger coil. �

As it happened this didn't work, but it did enable me to get the sludge cleaner running around the system quickly. �What I do is to open the valve and run the pump for a while to get things circulating. �After a quick cuppa, the valve is closed and I wait to see what happens. �Which on this occasion was nothing!

Windy

Title: Re: Hot Water Problem
Post by thescruff on Nov 6^th, 2004, 11:59pm

the mind boggles :-X

I want the other bits, like the cylinder connections, motorised valves, pump and the cold feed/ open vent connections.

scruff

Title: Re: Hot Water Problem
Post by Windy Miller on Nov 7^th, 2004, 11:21am

SS - Cheers for sorting out the pics Mate - think ther're big enough? I'd had a few beers last night and I must have sent you the wrong ones! I got the hump with it all in the end and thought Sod it I'm going to bed! I'll send you the smaller ones in a mo!

Scruff - Sorry to hear that your mind is boggling Mate! I misunderstood what it was that you wanted pictures of!

It is a very basic system - single pipe - no motorised valves - not even a room stat! The layout seems to be very much a a bare bones system that was done years ago to a limited budget.

It has worked fine for years and all I want to do is to keep it going for a little while longer 'till the old boy moves to a smaller place.

I am wondering if its more grief than its worth posting pics on here, so I may just go down the drain and flush route and if that fails get a central heating engineer in to sort it.

Cheers for your help any way Guys.

Windy

Title: Re: Hot Water Problem
Post by bstyle on Nov 7^th, 2004, 11:38am

It sounds like it needs an air vent on the primary flow top connection to the Hot water cylinder. This is the best way of getting the air from the system. It's not going to sort the entire system out but it is a start!

Is the boiler a long way from the Cylinder?

I've had jobs where it takes forever for the gravity circuit to circulate, it's normally down to air- certainley on the long runs of pipework.

You can always try holding a piece of hosepipe on the ballvalve and letting a bit of mains pressure down the cold feed to try and clear it.

Hope this helps