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Discuss Pressure reducing valve on boosted hot water? in the DIY Plumbing Forum area at PlumbersForums.net

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87
Afternoon everyone

I have gravity fed hot water - downstairs taps are 4.4m below tank. Upstairs 1.5m. The hot at the new minimum 0.3 bar monobloc kitchen tap is delivering a flow rate of just 4 L/min. So I am thinking about fitting a single impeller booster pump. This will be ideal for boosting hot water at upstairs and downstairs taps but I have an issue with the Bath/shower.

The issue is that both the hot AND cold feed to the bath are gravity fed from the loft tank. If I install a booster pump will the boosted hot then overpower the gravity cold at the thermostatic bath-filler/shower

If so then will fitting a pressure-reducing valve or gate-valve to the bath hot water after it has branched-off re-balance hot and cold to the bath/shower - or will the thermostatic part of the bath-filler/shower sort that out anyway? Any pointers will be gratefully received.
 
Messages
87
Need to boost the cold aswell so twin impella pump required
Hi ShaunCorbs - I'd love to do that but the 22mm cold feed to the bath goes directly from the tank to the bath filler. It is inaccessible anywhere else but in the loft. The hot draw-off at the top of the cylinder is a fair distance away down in the airing cupboard below (hence my idea of using a gate valve to rebalance)

To install a twin impeller I'd need to position it in the loft. Can I install a twin impeller to boost' the 22mm cold feed in the loft BEFORE it goes down into the bottom of the cylinder and connect the other impeller to the 22mm cold up there in the loft?
 
Messages
87
Hello ShaunCorbs

Thanks for the response. That ‘can’ be done but would involve taking a 22mm cold flow down inside the airing cupboard - up into the loft - through the pump - then back up again to reconnect to the 22mm cold flow to the bath filler. I can’t re-route the cold through the first-floor floor space as the bathroom floor is tiled. it will be tight for space in the airing cupboard.

The existing flow-rate is OK for a bath and the ‘drencher’ shower head isn’t used much. So would a possible work-around be to - Pump hot only from down inside the airing cupboard leaving cold to bath- only on gravity (cold to every other outlet is from mains) then to limit the pressure on the pumped hot to the bath with a gate valve so as to avoid pumped hot overpowering the cold at the bath filler?
 

ShaunCorbs

Staff member
S. Mod
Plumber
Gas Engineer
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27,332
Reroute from the tank down into the airing cupboard into the pump on the floor then back up into the loft to connect to the existing pipework

then do the same with the hot eg off the cylinder with an s flange then into the existing hot pipework but modifying the vent correctly

can’t throttle the hot as you will burn the pump out
 
Messages
87
Reroute from the tank down into the airing cupboard into the pump on the floor then back up into the loft to connect to the existing pipework
then do the same with the hot eg off the cylinder with an s flange then into the existing hot pipework but modifying the vent correctly

can’t throttle the hot as you will burn the pump out
Cheers SaunCorbs

Never would have occurred to me about pump burn-out.
S- flange Is that a Salisbury Flange? Modifying vent correctly? I think I need to call in a plumbing professional!

In all honesty I think you have convinced me that this project is beyond my diy skills and best left to the professionals. That in itself is good-progress. Thank you.
👍
 

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