The shower in my (1930 built) house is fed direct from the bath taps. The hot water cyliner is in the airing cupboard.
The hot water pressure is very low, not just in the bathroom but in the kitchen as well.
This makes the shower difficult to use as mixing even a small quantity of cold water with the hot makes the shower go cold.
Should I fit a pump somewhere to boost the flow of hot water from the cylinder? If so, where?
A pump located under the bath would be a possibility. *But* you will also need to plumb in a low pressure cold feed from the cold header tank rather than using mains. The 2-gang pump will then receive hot and cold at roughly the *same* pressure, and boost them both equally so that your mixer shower will work properly.
The purists will also tell you that you should take the hot feed from a Surrey or Essex flange installed in the hot cylinder rather than just using the default take-off at the top. However, you can probably get away without doing that - as I do.
Thanks Roger.
does the Surrey/Essex flange boost the pressure of the hot water?
It sounds like you have gravity fed hot and mains cold at the bath. If this is the case you may be able to help the situation with a single impeller pump bosting just the hot. The better but more difficult alternative would be installing a new dedicated cold feed from the cold water tank and using a dual impeller shower pump.
Actually, provided you use a pressure balanced mixer, it is entirely possible to mix mains cold water with pumped hot water. You simply need a good mains flow rate and a single impellor pump. I fitted such a system into my last house and it worked admirably.
In fact, even without a pressure balanced mixer, it will probably still work very well, but may be a little sensitive to other taps/toilets being used in the house.
Indeed. I fitted mine without a flange, but understood that one might be required if it sucked air. It didn't. However, my cold tank was directly above the cylinder with flowed bends. A 15mm tortuous feed with elbows would be another matter.
The best place for the pump is need the cylinder, as they prefer to push rather than pull. It also means that the kitchen hot tap gets pumped operation, too.
Christian.
This sounds like a good idea.
Is it just a case of fitting a single impeller pump in line with the hot water cylinder outlet? That would (presumably) boost the hot water pressure to all taps in the house. Or should I fit the pump in line with the feed to the bath/shower?
No. It just takes the water from a bit lower down in the cylinder. Otherwise, if you have a very powerful pump, it can suck water - followed by air - from the vent pipe, rather than water from the cylinder. A flange prevents this - but isn't always necessary, depending on the power and location of the pump.
This is an alternative to the twin-impellor pump which I suggested earlier, and involves less plumbing, but doesn't give equal hot and cold pressures - which may or may not matter.
As far as location is concerned, you can choose how many of the hot taps you wish to boost, and put it in an appropriate place to achieve this. The pump will probably be heard throughout the house - which may be a consideration.
[The normal way in which these pumps work is that they have a flow switch, which detects (gravity) flow when you open a tap, and switches on the pump. When you close the tap, the flow stops and the pump is automatically switched off].
If you read and understood Christian's post this would all be clear. Using one in-line pump on the DHW draw-off of a low pressure cylinder and the cold to all taps via the mains can give equal pressure at the taps for mixing. You install a 22mm pressure equalising valve after the pump, then both hot and cold lines are at equal pressure. You could fit a few 15mm equalisation valves on a few lines rather than a 22mm valve.
Assume: the pump gives out 1 bar, the mains 2.5 bar. When you turn on the cold tap 2.5 bar is there. Then you turn on the hot and the cold drops to the same pressure as the hot that is flowing through the equalisation valve. If someone flushes a toilet and the cold mains pressure does not drop below
1 bar, then no affect.The idea is not to have an adverse effect on the shower mixer, the most critical part of the water system. If a separate shower en-suite shower and someone turns on a bath tap then the pressure is going to drop along the pumped DHW line. It mat be best to take the bath from the top of the cylinder and the rest of the taps and shower from a Surrey flange. Then the bath will not affect the pumped supply. If the bath water from the mains then fix a low pressure hot water mixer on the bath
The Grundfos single impeller Booster pump is quiet, and cheap (about £80) its selling point.
Thank you all for your quick and useful replies.
I'll put a single impeller pump on the outlet side of the hot water cylinder and let you know how it goes.
thanks again!
Using a pipe stat and return loop pipe on the DHW draw-off back to the cylinder, a secondary circulation loop can be added very easily using the same pump. The return pipe only need be very small bore plastic to thread through joist, etc, just like cable.
Check if the mixer has an integral pressure equalisation valve. If not put one in directly after the pump.
In fact, you would want it very thin, as you don't want the secondary flow to reduce the outlet pressure. Obviously, you can also balance it down with some sort of valve, too.
I can't help thinking that a single impellor shower pump would be too noisy for a secondary loop installation, though. Some might not like the low flow rate and high pressure drop when no outlets are open.
Christian.
The Grundfos Booster is quiet. It looks like a normal CH pump.
ge
Thanks for that IMM and Christian. This Grundfos pump sounds a god alternative to a big power shower pump. Another post to be saved.
What for? Half the information is totally wrong.
Regards Capitol
Can someone confirm for me please that the Grundfos Booster pump mentioned here should be in a 'push' configuration rather than 'pull'. I was under the misapprehension that this type of pump should be fitted near the outlet, but I am now seeing comments indicating fitting it at the tank end - this would be a far better set-up for me and far easier to implement.
Rob
Pumps fundamentally prefer to push. You would have to go out of your way to design a pump that prefered otherwise.
One problem with pulling is that you only have 1 bar of pressure before you get a vacuum. Use much of this pressure loss through pipe losses and you will get cavitation and other nasties. 1 bar doesn't pull much water if there is much restriction, such as long lengths of pipework or elbows.
No pump after the restriction can overcome this issue. However, if a pump is before the restriction instead, the only pressure restriction is that of the pipework rating. Therefore, you can push with up to 6 bar pressure, which can lead to a much higher potential flowrate.
Christian.
Capitol wrote
You've beaten it - *all* the information in your post is totally wrong.
I wonder what the sycophant doesn't understand.
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