No hot water from taps

[DaveF]

I have an open vented system. The flow of water from my hot taps lessened over a few hours and then just stopped. There is no hot water coming from any hot tap. All cold taps are working.

Initially I thought this was an airlock. But I have forced mains water from the garden hose pipe back through every hot tap. There is no burbling and the hot water does not start to flow through.

The cold water loft tank is full. The hot water cylinder appears to be full. I have blown back through the open vent pipe at the cold water tank which runs from the T junction above the hot water cylinder to the cold water tank. The air does not go into the cylinder but bypasses it and comes out of an open hot tap. So the pipe appears to be clear.

In the cold water tank in the loft the inlet to the downpipe at the bottom of the tank which is the cold water feed to the hot water cylinder appears to be clear.

I have a power shower which takes water off the hot water cylinder from a different outlet to the taps, at about 3/4 of the way up the cylinder. (The tap outlet is at the top). However when I do this I "think" it creates a gap at the top of the hot water cylinder as at this point I can then force water from my hose pipe back though a hot tap and I can feel the water outlet pipe at the top of the hot water cylinder go cold and water splashing into the tank.

i am not a plumber, just a DIY guy. My guess is that there is not enough pressure to push any hot water out of the top of the hot water cylinder to the taps. This may be caused by a blockage in the cold water feed, as the hot water cylinder is not refilling quick enough to keep it full and maintain pressure. The blockage may only be partial as the tank appears to be full, but could be filling slowly.

I would be grateful for any advice as to whether you think this is the issue or whether it could be something else. How do I confirm this. What is the best way to clear a blockage.

Thank you in anticipation of your help.

DaveF

 

[Riley]

I’d be looking at airlock. Has someone had a really long shower and the tank in the loft has drained completely?? How well does the ball valve on the tank fill??

 

[ChippyCal]

Check power to cylinder, is water flowing but just cold?

Turn off isolator on your hot water out feed, undo the joint after the isolation, place a pipe to bucket, check if water is flowing / hot, if no water is coming out of cylinder and power is ON, it could be a blockage if cylinder is full and you know the issue is with the cylinder.

 

[Riley]

I’d still be leaning towards airlock

 

[Aire]

Does the power shower still work?

 

[Harvest Fields]

Didn’t the OP say no flow through hot taps? This would be a stuck/blocked gate valve possibly? Sorry if this has already been mentioned. It has been a very long day.

 

[Aire]

Didn’t the OP say no flow through hot taps? This would be a stuck/blocked gate valve possibly? Sorry if this has already been mentioned. It has been a very long day.

I was thinking that or scaled up cylinder inlet/outlet. I was waiting for a reply to whether his power shower still works or not to decide if it's an issue with water in or out of his cylinder

 

[DaveF]

Thanks for the replies. I don't think it is a limescale issue as the water is softened and I don't think it is an airlock as I have forced water back through every tap and there is no gargling sound. I don't think the tank in the loft has been emptied. It fills quite quickly but it is still possible to drain by overuse of the power shower. My daughter did this years ago and caused an airlock which I removed using a hose pipe to force back though a hot tap.

The power shower is fed from a pipe 3/4 up the cylinder, not the some as the hot taps, which comes out of the top. The power shower does work, although I have not run it for a long time. If the water in the tank is not refilling quick enough I didn't want to run the level in the tank below the power shower pipe.

By gate valve do you mean the stopcock type tap that sits on the down pipe from the cold water tank to the cylinder? This was open. It also turns fine.

With reference to Chippy Cal reply, I am not sure what you mean by power to the cylinder. My system is gravity fed.

Thanks to you all for your responses.

 

[Harvest Fields]

Thanks for the replies. I don't think it is a limescale issue as the water is softened and I don't think it is an airlock as I have forced water back through every tap and there is no gargling sound. I don't think the tank in the loft has been emptied. It fills quite quickly but it is still possible to drain by overuse of the power shower. My daughter did this years ago and caused an airlock which I removed using a hose pipe to force back though a hot tap.

The power shower is fed from a pipe 3/4 up the cylinder, not the some as the hot taps, which comes out of the top. The power shower does work, although I have not run it for a long time. If the water in the tank is not refilling quick enough I didn't want to run the level in the tank below the power shower pipe.

By gate valve do you mean the stopcock type tap that sits on the down pipe from the cold water tank to the cylinder? This was open. It also turns fine.

With reference to Chippy Cal reply, I am not sure what you mean by power to the cylinder. My system is gravity fed.

Thanks to you all for your responses.

Yes to the gate valve/stop tap. It will normally have a wheel head on it. When you say it turns? Does it keep turning both ways or does it stop?

 

[Riley]

Something has changed. As per harvest above has any work been done. Any valves closed??

 

[DaveF]

I have located the gate valve on the down pipe. It is open. It does turn both ways and stops both ways.

Absolutely no work has been done. All valves are open. The flow of hot water to the taps decreased over 12 hours and has now stopped for several days.

I ran the shower for a short while (which comes off the cylinder at 3/4 height) and the cold water tank in the loft started to refill. So I presume the downpipe is not blocked.

I used my pressure washer to blast water up a hot tap, but this had no effect either so I doubt this is an air lock.

It is as if there is a blockage in the pipe at the top of the tank where hot water flows out to the taps. This is a short pipe which then joins to a vertical pipe, which goes up to the cold water tank (ie this is the hot water cylinder overflow) and down to the taps. I have blown down the overflow at the tank and air passes directly out of the tap. So the main pipe is not blocked. No water is flowing across this short piece of pipe at the top of the cylinder.

Unfortunately I do not have an isolation valve on the hot water out feed so I can disconnect the pipe and prove my theory.

Does anyone have any ideas how I can clear a blockage if it is in this short pipe?

I am thinking I may have to shut the gate valve on the downpipe, run the shower to drain some water off the tank and then do one of two things:

1. Open all of the taps and send water back down the overflow pipe, from a hose or pressure washer until water is running. Then shut the taps as the only place it will have to run is back into the tank
OR

2. Undo the nut at the top of the tank which is securing this short pipe. My concern is that the copper pipe is not flexible and I may not be able to get it out of the tank. I don't know how far it goes in.

Thanks for your continued help.

 

[Harvest Fields]

If the gate valve is working then it is either an air lock/blockage. Is the power shower getting hot water? Or just cold. Sorry if you have answered this already.

 

[Aire]

Isolate cold feed into tank, run shower to empty a little water out the tank. Crack the top nut on the cylinder and have a look inside, you may have to cut the horizontal pipe and re attach it afterwards.

 

[DaveF]

The power shower is drawing hot water.

I am a bit nervous about cutting the pipe. I will probably get a plumber friend in to do that an also get an isolator valve fitted at the same time.

What do you think of the option to send mains pressure water back down the overflow pipe from the loft as I documented earlier. This would save cutting any pipes.

 

[Aire]

Not the best idea, if it's scale you won't budge it anyway.

 

[Harvest Fields]

Can we have some pictures of the pipework in the airing cupboard please.

 

[DaveF]

I don't think it is scale as the water is softened. The cold water tank is 18 years old but the inside is like new. No scale at all. This option would save the need to cut the pipe.

 

[Riley]

Plus don’t put an isolator on the horizontal as it can be shut off meaning the cylinder cannot vent

 

[DaveF]

What do you think about pushing mains water back down the open vent as I detailed earlier? Once the pipes are full to the taps the only place for the water to go is across the pipe into the tank, which I would partially drain by running the shower for a short while.

Attached are 2 pics. The horizontal pipe at 3/4 height feeds the shower.

 

[Aire]

The trouble with forcing water down the vent is if it does shift whatever is blocking the outlet, all you are doing is forcing it back into the tank. You need to remove that top connection to see what's going on.

 

[Riley]

Were I in your position I’d be giving serious thought to getting a pro in dave. I wouldn’t look at blasting it all backwards with mains there may be no blockage in which case you run the risk of overflowing your cwsc as it back filsid be more tempted to drain the cwsc, drain the cylinder down to the point of the shower draw off then take apart the pipework off the top off the cylinder. You have plenty to play with there in terms of movement

 

[DaveF]

Hi Riley. You are right. I have got my plumber coming tomorrow. I will post the outcome. Thanks for your advice

 

[DaveF]

After some further tests we determined that after the shower was used, the hot water cylinder was not refilling as quick as it should have been which indicated a blockage in the supply pipe from the cold water storage tank. So we closed the closed the isolator valve on the downpipe and disconnected the pipe below it. Blowing into this pipe cleared the blockage (which was probably an air lock after all). We now have hot water again. Many thanks for your help

 

[Harvest Fields]

Thanks for the feedback.