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Lost pressure from hot water :(

Postby StrangerUK » Sat Apr 05, 2008 1:54 pm

Hoping someone can advise on a plumbing problem. I have no plumbing knowledge so apologies for describing this in laymans terms. Just had a trusted and experienced plumber fit me a new bathroom suite with mixer taps. Once installed, hot water pressure is very poor – a slow stream of water from the basin and bath mixer – too slow to fill a bath. Prior to the change, pressure wasn’t exactly great – didn’t have much force behind it, but is certainly worse now. We’ve always had decent cold water pressure, but oddly the cold now seems to have more pressure. The wife think its directly related, like some of the hot pressure has somehow ‘transferred’ over to the cold, but I can’t see how that can be as I think the cold/hot are on two different ‘systems’.
We’re in a flat, with the hot water cylinder tank (immersion heater) in the airing cupboard just a couple of metres away from the tap outlets. We have no loft, so no cold water tank. Followed the incoming water feed past the stopcock and think the cold water is directly from that feed.
My only thoughts to resolve the problem is to buy and have fitted a pump, perhaps located next to the hot cylinder tank to boost the pressure to the basin and bath.
Is there a problem somewhere that is causing the poor hot pressure? Would a pump solve it?
With thanks,
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Postby htg engineer » Sat Apr 05, 2008 5:39 pm

The difference in the cold water pressure will not affect the hot water pressure - the cold water flow rate may have increased if he has opened the mains stop tap slightly more than it was previously - nothing to wory about.

The hot water pressure could be a couple of things,
The cylinder in the cupboard - is there a tank above it, check the ball valve is opening fully, check the ball valve is not getting stuck on the side of the tank - if he drained the hot water then it could be the ball valve at fault - the fact you're in a flat with no loft - the hot water pressure will never be brilliant, unless you:
a) pump it
b) install a combi boiler

Just because there is a lack of head, that is required to push the water through the cylinder with force.

The other factor that could be affecting the hot water is if the gate valve before or after the cylinder has been closed it could
a) not be fully open
b) quite common for the gate valve spindle to sheer off

Check any isolation valves that were fitted to the water pipes for the bathroom are fully open - did he use flexi hoses ? copper pipe is best.

Hope this helps
htg engineer
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Postby christhemario » Sun Apr 06, 2008 7:30 am

Hi, just a thought that you may have an air lock in the system as you have no "Head" of pressure, try connecting the two taps together using a washing machine waste pipe ( has two rubber end caps) and turn on the hot and cold at the same time for about 20 seconds then try the hot tap again this if there is a lock will release it. Good luck!
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Postby StrangerUK » Sun Apr 06, 2008 8:27 am

Thanks for the reply, sounds good stuff.
Yes, I think we have one of those 'combination cylinders' where there's a cold water tank with one of those floating ball things inside.
Confident to say the plumber didn't do anything with the hot water cylinder, but I've just checked it and all seems to be well - that floating ball thing looks OK, the cold water level is sitting where it always has been, and I found on/off valve turning thing, which I've made sure is fully open.
He has installed those isolation valve things before each tap. Just checked to make sure they are fully open, but still no change to the pressure. Looked underneith - he's used copper close to the basin and bath, then one of those isolation things then flexi hose up to the taps. I think the hoses look OK - they look the same size as the pipe they're coming off and have no kinks/bends/angles in them.
You're right - even prior to the new bathroom, hot pressure isn't been great. I like the sound of a pump, as would be nice to have a bit more go in the water. The cylinder is sitting behind the airing cupboard shelving, and the bottom shelf is about level to a curve in the hot water pipe coming out of the cylinder. Do you think I could have a pump sitting on that bottom shelf, and plumbed into that copper hot water pipe from the cylinder? Hopefully that would boost it to all outlets - the bath, basin, and kitchen?
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Postby StrangerUK » Sun Apr 06, 2008 4:03 pm

hi chris, sounds interesting, think i got a spare hose in the garage to use - will try it later today and let you know what happens!
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