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No Hot Water After Draining Cold Water Tank

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boobesque | 08:39 Sun 30th Jun 2013 | DIY
5 Answers
Hello

As the title states I drained my cold water tank to install a new shower and new taps in the bathroom. When I filled the cold water tank again water is coming out of both cold and hot taps but no hot water.

Have a hot water tank and I left the boiler heating water for 4 hours and all I get is about 1 minute of luke warm water then it goes cold. The pipes to the hot water tank are really hot and the hot water tank itself feels hot.

I've been googling but can't find a solution. The water tank has a vent that goes back into the cold water tank in case of over pressure. Central heating works fine and when I turn on the hot water timer I can feel the pump working. The pump and boiler are only 2 years old so I don't think they are the problem.

Any ideas? I spent an hour filling a bath with the kettle yesterday and I really don't want to do that again.

Thanks

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Not sure. The hot tank is filling from the cold is it ? If not you won't warm up much. Maybe there is an air lock between the two ?
Question Author
When I get home today I'm going to drain the hot water tank and let it refill with fresh water. If that doesn't work I'm going to force cold water from the mains through a hot tap into the hot water tank.

And yes the tank fills from the cold water tank in the loft and gets heated after. No immersion heater on the tank either. There is one but it's never worked from when I moved in
Dd you do the installation yourself? If not, I'd get back in whoever did it.
Question Author
Problem solved. I tried to force water through the hot tap and flooded my bathroom so I gave up on that and started draining the cold water tank again by tieing the ball cock up and turning on the cold taps in preparation for draining the hot water tank. When the water level got below the hot water tank overflow outlet (which was submerged) bubbles started coming out of the feed pipe. I stopped draining the water and tested the hot tap. It was hot. Damn hot. So I'm guessing it was something to do with an air pocket. I still don't see how air would stop only the hot water and not the cold but it seems to be working so I'm not going to tempt fate and try to recreate the problem for educations sake alone.

Thanks for the help
Boobs......... I've been out all day, so I've only just seen this. I'm sorry I couldn't have told you earlier that you had an air lock.
Very common after filling a gravity system. The cold goes straight to the bath from the roof tank, but the hot has to go through the immersion cylinder.

Ether blowing down it, or cross-connecting to the mains usually sorts it out........ as you have found for yourself :o)

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