lack of hot water presure


Postby 'tap ead' » Wed Nov 11, 2009 5:49 pm

Hi all

hope you folks can help recently re-plummed a house after a flood , but now when we turn on the hot taps ,which are run via a combi, the presure drops significantly more worrying is when you turn on the cold tap at the same time the hot virtually stops ! The combi has'nt been touched at all,so at a loss HELP !
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Postby plumbbob » Thu Nov 12, 2009 11:48 pm

Most likely possibilities are the mains from the street are too low, one of your stop taps is not fully open or your new pipework is restricting the flow of water.

Really it's all guesswork because of the limited information you have given.
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Postby 'tap ead' » Fri Nov 13, 2009 12:31 pm

[quote="plumbbob"]Most likely possibilities are the mains from the street are too low, one of your stop taps is not fully open or your new pipework is restricting the flow of water.

Really it's all guesswork because of the limited information you have given.[/quote]

cheers plumbbob , the water board have changed the mains stop tap but it does seem a bit light on presure at the cold tap,is there any way of checki the flow presure at the tap ?
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Postby plumbbob » Fri Nov 13, 2009 5:52 pm

You need to do both a pressure test and a flow test to see what's going on. Obviously, it is best to use professional equipment, but if you don't have any there are simple DIY tests that will at least give you an idea.

When there is no water being used in the house, put your thumb over the cold tap nearest the incoming main and turn it on. Use both thumbs/ hands if necessary and try to stem the flow. As a general rule of thumb (oh, I'm so sorry), you probably shouldn't be able to stop the water. If you can just, it's possibly maybe alright. If you can stop it easily, something is wrong.

Now do a flow test by seeing how quickly a 2 litre pop bottle can be filled. Any time longer than ten seconds is poor.

If the pressure test is good but the flow poor, it may be caused by scaled up pipes. (Do you have a de-scaler?) If the pressure and flow are poor you need to contact the local water company who will test it free as it could be their mains at fault. They do have a sneaky policy of reducing mains pressure to reduce consumption and leakage until someone in the road complains. Then they go and turn it back up again!

Low pressure to taps could also be bad news because it is a symptom of a burst underground main.
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