limited hot water, rads are fine

[ben444]

I have done some work on my heating system and now have a problem with the hot water.

Firstly, the problem; If I turn the hot water on then everything works and the storage tank pipes get hot. And hot water is present quite quickly. However if I turn a hot tap on the pressure is very low, you wait for it to get hot which it eventually does, but by this time it has slowed to a trickle and then stops completely. The power shower fairs a bit better as it is pumped: You get about 2 minutes of water before again it runs out of water.

It seems that the storage tank has plenty of hot water in it, but that there is no pressure in it. You can use some, but then you will have to wait for some pressure to build up.

Secondly, how I got to this point: This is an indirect boiler system. The pump next to the storage tank had failed so I decided to replace it, although I am not a plumber. I replaced the pump which fixed the problem, I now get heating which I didn't get before. I have done some searching on the internet and have checked that the coil has not got an air block, there is a bleed pipe which I undid and immediately water came out.

Can anyone suggest why whilst the boiler seems to be working perfectly I can only get some of my hot water out of the storage tank and at a much lower pressure than before?

Any help much appreciated.

 

[twgas]

Sounds like an air lock in the draw off.

 

[ben444]

Thanks for your response. I reckon it is some sort of air lock as there is some spluttering before the hot water runs out. If it was debris then it wouldn't sputter I am guessing.

what I don't understand from your post where such a draw off might be located. I have loosed the draw off already (as stated) for the heating coil return. This was located just as it came out of the boiler.

Would you have any idea where this other draw off that you mention might be located?

 

[twgas]

The draw-off is the supply from HW cyl to the taps, if the cylinder is heating there is nothing wrong with the coil.

 

[ben444]

Thanks for that. I will follow the hot water feed coming out of the top of the HW tank and look for any draw off taps that I can bleed. Won't be able to do this until Friday. Will post back if successful.