Poor hot water pressure - grundfos booster pump cure?

[jamin008]

Let me start by saying I am no plumber. A competent DIYer but not a plumber so thought I would ask the experts.

I have fitted a new bath, basin and taps this weekend. The hot water pressure was poor prior to fitting and I suspected fitting new 1/4 turn taps would not help the situation and I was correct, the hot pressure is now appalling and we cant shower! The cold supply is mains and when I put both the hot and cold on full the pressure is less than with cold only. Im guessing the cold is going back up the hot pipe? Doesnt sound good to me!

The system is as follows...
1st floor maisonette with loft
Back boiler in lounge
Large vented hot water cylinder in lounge cupboard
Cold water storage tank in loft feeding the hot water cylinder only
3/4 inch hot pipe from cylinder around house (kitchen sink, bath and basin only)
Cold is mains throughout the house

Can I fit a pump in the loft to boost the hot water pressure to the hot taps? I only need to boost the hot water, the cold is fine. To be honest the bathroom is the only room thats suffering from low pressure as ive fitted minimum .5 bar taps but im assuming it wont do any harm to boost the whole system?

I have heard that I can use a Grundfos UPA 15 90 booster pump which typically adds 0.5 -0.75 bar but I have mains cold water, will this cause a problem due to the large pressure difference even once the pump fitted? Also it is a vented cylinder so im concerned that if I pump the hot from after the cylinder it will either pump out of the vent or suck air through the vent? would that be the case?

As you can tell I am an amateur. Any advice greatly received to fix this problem.

 

[jamin008]

Ive done a bit more reading and I have used flexi pipes from the check valve to the tap which i now understand probably hasnt helped either!?

 

[unguided1]

Install a single impeelar booster pump, I would suggest using it therough either an essex or surry flange though, because if you install it straight onto the hot outlet you could end up drawing air down the open vent, causing cavitation on the pump and shortening the life span of the pump

 

[jamin008]

To install the surry flange I would have to fit the flange to the cylinder and a new vent pipe from the flange to the tank and also adapt the current pipe from the cylinder so it no longer vents?

This is beginning to sound expensive as I would have to do all this and buy & fit the pump. The pipe all the way from the tank to tap is 3/4. it only drops in size where I have fitted the flex pipe. I would say the cold water storage tank is 2m above the shower head. Would you think that would give enough pressure for a low pressure mixer shower if I ensure all hot pipework is 3/4 or 22mm and I fit some sort of pressure reducing device to the cold?

 

[unguided1]

If you install a surrey flange the vent pipe goes into the top tapping the hot water outlet comes out of the side tapping this item is designed to allow air out through the vent pipe.

 

[SafeGasInstall]

flex go and check it visual as is not over turn or kinked

 

[jamin008]

Ive checked the flexi pipe and its not kinked. Its only 13mm internal diameter so im going to buy some semi rigid plastic pipe and fit that hopefully that should increase the pressure somewhat. Im also going to source some .2 bar taps (the ones I have are .5) so hopefully that will cure (or at least better) the problem.

thanks for all your help. I will update later today regarding the pipe. The taps will have to wait!

 

[pobsdad]

You mentioned check valves.If the taps are seperate,you won't need these,and they will cause a huge drop in flow rate.

 

[SafeGasInstall]

Water regs !!!

 

[jamin008]

Ended up using copper pipe. Did a quick calculation and after fitting the inserts to the plastic pipe you would probably lose 1/2 the internal area compared to copper so the flow would be pretty restricted. Anyway, made all these alterations and sod all difference! Then I removed the check valve and checked the internal diameter of that. Its bigger than the compression fitting I would have replaced it with so that would make no difference anyway.

So decided that tomorrow I will but some low pressure taps from a local merchants. Any suggestions of a good one? Was thinking Grahams or the Plumb Centre but where is generally cheaper? Im in Colchester, Essex.

Thanks for all you help. Thanks given.

PS what was the reference to water regs? Am I doing something wrong?