Home Plumbing advice required - SERIOUS

Here's a nasty little 'un for anybody in the know when it comes to domestic plumbing..........

.....A few days ago the hot water (tanked) pressure dropped quite dramatically at ALL outlets and has not returned. A FULL hot bath normally takes only about 5 minutes to run, but is now more like half an hour.

Having checked the cold (mains) pressure, I can say that it is fine. I drained the whole hot tank and the cold (loft) tank after switching off the cold main. The cold storage cistern in the loft is fine as far as I can see, and in fact got treated to a real good clean out whilst I had it all uninsulated and uncovered. Nothing too nasty lurking in there really.

After refilling the system and waiting an hour or so, it's as bad (probably worse) than it was. The bath and basin taps now run for a few seconds and then STOP.

I'm in a soft water area (Glasgow) and the majority of the pipework in the house is stainless. Anything left is all copper.

Any ideas folk?


Garry

[embee]

try a note on this forum

http://www.screwfix.com/talk/forum.jspa?forumID=25

Sounds to me like there's a blockage in the feed between the cold storage cistern and the hot water cylinder, or possibly at the cylinder outlet, my guess would be the feed.

Is there anyway you can isolate it off so that you can temporarily stop water refilling in to the hot water tank? (You could tie up the ball valve in the expansion tank perhaps) If so do that then drain the tank some way. Then re open and allow the system to refill the tank naturally once more. You should be able to here the tank refilling at a reasonable rate. If not there is a partial blockage on the inlet side.

If it refills well then the problem would appear on the outlet side of the hot water tank. It is a matter of tracing back all the way to the tank. If you turn the tap nearest to the tank on in the bathroom is there a reasonable flow? If not then the problem is somewhere between tank and taps. it could be that the outlet of the tank itself is partially blocked. That could either be by some foreign body getting in there or the outlet port itself could be furred up with calcium.

If you can drain the tank as much as possible and tie the ball valve up to stop it refilling.Then undo the pipework where it comes off the tank, you might be able to spot the problem.

If any other questions feel free to pm me.

well said Peter couldn't put it better myself, except to say if the ball valve is tied up on the header tank then the hot cylinder is drained down then a short piece of hose pipe can be connected from the cold tap to the hot tap and the hot pipe work can be back flushed.

we have this sometimes, the plummer showed us how to fix it.

called an air-lock that happens.

dunno if it applies to you, but something for you to try anyway.
get a towel and hold it over the hole the water comes out of on your bath tap.
then turn the hot and cold water on at the same time, stopping the water coming out with the towel.

hold for about 10 mins, and sorted.

worth a try i suppose

[timwilky]

The obvious thing to check.

The pipe from your cold storage tank should feed into the top of your hot water tank. Now normally there is a gate valve in this pipe, once turned it forms an air lock preventing hot water from running out of the tank. You get enouth water running out to form the vacuum and then nothing.

Check no one has mucked about with it


Bikeageboy is correct with his cure for a conventional air lock assuming of course you have a mixer tap and therefore by blocking the cold out which is under pressure you divert it back into the hot water fedd which is much lower pressure and blow any airlock out into your hot water tank. Be careful, and don't overdo it or you will pressurise the tank. you don't want to know what all that hot water could do if the tank suddenly split.

Originally Posted by timwilky

The obvious thing to check.

The pipe from your cold storage tank should feed into the top of your hot water tank.

Sorry Tim, but it really doesn't do that! The feed from the cold water tank in an indirect system always goes into the BOTTOM of the hot water cylinder. The head of water (ie, the water in the higher cold tank) then forces the hot water out of the TOP of the cylinder.

So logically, either you don't have water entering the bottom of the cylinder at full head, or you have something stopping the hot water coming out of the cylinder. As you say it affects ALL taps, which we presume to be kitchen sink and hand-basin, if it isn't the former (ie the feed into the hot cylinder), it'll be something close to the outlet of the cylinder, before it branches off into the different various hot feeds.

Can only guess what that will be though, but my personal guess would be a foreign body on the inlet side of the cylinder, perhaps lodged in a valve. I presume the system hasn't frozen up?

Originally Posted by El Boccadillo

The feed from the cold water tank in an indirect system always goes into the BOTTOM of the hot water cylinder. The head of water (ie, the water in the higher cold tank) then forces the hot water out of the TOP of the cylinder.

You are quite correct there sir however the majority of hot water tanks in the UK have a connection for the cold water feed at the top of the tank (this is however connected to a pipe inside the cylinder that goes to the bottom ) I hasten to add not ALL are like this.

it is releatively easy to identify the cold feed (it's bloody cold for one )

I concur with the blockage is most likely at any stop valve in the system as this is usually the smallest orifice in the system, likewise though it could be at the outlet of the tank (if something has indeed Floated )

I would however fix up the ballcock and slacken the outlet of the tank then having an acomplice allow the tank to fill whilst you watch for water at the outlet (have a towel handy and someone ready to stop the cold header and turn on a hot tap if sufficient water comes out unimpeded then start tracing through the outlet side for valves.

should there be insufficient water flow then look towards the inlet side.

hope this helps (and hasn't just confused the matter further )

what type of system are you running??

if its a un vented system the pressure vessel in your hot water tank might have gone..

Alex

Just a note to say "THANKS" to all for the input. Wanting to avoid draining the whole thing down again and splitting all the joints to look for a blockage, I back flushed the system a little via the mixer tap in the kitchen (which is fed with mains cold). I turned up the pressure and (using the middle position), blocked off the outlet to create a current back up the hot pipes.

Seems to have done the trick, since the next day the downstairs toilet hot tap dispensed a whole batch of real sludgey piping hot water at good pressure. All hot lines are now pumping it out in fine style.

That saved a lot of time and hassle. Will keep an eye on how it all runs.

Thanks again,

Garry