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Feb 23, 2019
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Member Type
DIY or Homeowner
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
 
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
 
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
 

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