Shower pump and pressure reducing valve

[diypeteski]

Hi all, new to this site so hope I've posted this in the right place.

I've recently installed a pressure reducing valve http://www.plumbworld.co.uk/pressure-equalising-valve-344-20563 to equalising fairly decent mains and pretty poor hot pressures. Unfortunately the thermostatic mixer shower pressure is still no better so I'm now thinking of simply adding a twin impeller shower pump.

My question is if I do this I am still effectively connecting the mains supply to a shower pump. Is this a big no no and if so has anyone got any other "cheap" options?

Thanks in advance

 

[Rob]

You cant pump mains water plus if its that good you wouldnt need to.

You could try getting a single impellor pump on the hot (assuming you have stored hot water and suitablely sized tanks) and match it to the pressure of the cold water.

Your reducing valve should do the rest

 

[diypeteski]

Thanks for the quick response Rob.

The reducing valve is connected to both mains and hot and I think the theory is they balance each other out without being mixed.. or something like that The problem is that it's reduced the cold to an unusable flow rate now.

I guess I could remove the reducer (to regain the cold flow) and, as you say, just put a single impeller on the hot.

Will I then have an issue with connecting a pumped hot feed and a cold mains feed to a thermostatic mixer?

 

[Charnwood]

The reducing valve is connected to both mains and hot

You have a pressure equalising valve, not a pressure reducing valve. Totally different beasts.

 

[diypeteski]

My mistake, thanks for the clarification Charnwood.

So does that makes things easier in this situation:

a) am I now able to fit a twin impeller shower pump to both sides of the equalising valve or is that still a bad thing to do

or

b) do I remove the valve completely, fit a single impeller to the hot, hook up the standard mains and boosted hot to my thermostatic mixer?

 

[picasso]

get rid of the equalising valve, do a search for venturi shower and if you dont like that idea then put in a twin pump running the cold off the tank in the loft (if its big enough).

 

[diypeteski]

Hi Picasso. Not going to work unfortunately as the cold supply upstairs is one of these old fashioned style integral jobs.... tiny cold water supply that fills the hot water tank and the central heating expansion tank.

I really don't want to get involved with playing around with that tank at this stage as I've just refitted and retiled the bathroom. All pipes are now nicely hidden away with the pipes under the bath ready to receive a pump or whatever solution I can come up with.

Any more suggestions?

 

[muggles]

You can't put a pump under your bath, you'd need to put the pump in your cylinder cupboard with a dedicated connection from your cylinder. It sounds to me like you've got mains cold and a standard low-pressure hot water cylinder running your shower, this is almost always a no-no and you either need to run a new pumped supply as above, or change the cold to a tank-fed low pressure to the shower.

 

[echoes]

Thanks for the quick response Rob.

The reducing valve is connected to both mains and hot and I think the theory is they balance each other out without being mixed.. or something like that The problem is that it's reduced the cold to an unusable flow rate now.

I guess I could remove the reducer (to regain the cold flow) and, as you say, just put a single impeller on the hot.

Will I then have an issue with connecting a pumped hot feed and a cold mains feed to a thermostatic mixer?

Depends on how tolerant the mixer is of unequal hot and cold pressures.

If you pump the hot, the Pressure Equalising Valve will give you cold at the same pressure as the hot, which mixer showers need to operate properly.

With a single impeller pump, unless it is a 2-3 bar model, you would still need to reduce the mains cold pressure either with a PRV, which can work (it's what I have and it's good), or with your current equalising valve, which will match it to the hot pressure.

If feasable, the better soluton is a twin impeller pump on tank fed H & C supplies as previously stated.

 

[diypeteski]

Thanks Echos. So I take it my idea of combining mains cold and gravity fed hot is "allowed" if I can equalise the pressure?

If yes then I guess this configuration would work //www.diynot.com/network/diypeteski/albums/

 

[echoes]

That can work. Make sure your hot feed is a separate feed from the tank using Essex/Surrey etc. flange.

I have the same set up, but just using a PRV on the cold mains to provide an approximate equalisation of pressures, which my mixer works happily with. It wasn't my preferred choice though, but running a new cold gravity feed to the pump was not on.

 

[diypeteski]

Yeah same problem here. Also, the tank in the loft is some kind of wierd and wonderful design that includes a tiny cold water top up unit, the hotwater tank and the expansion tank for the central heating. Very old I would say and I had no intention of playing with it.

Thanks for the info Echoes (and all). I'll give it a go and see how I get on.

 

[echoes]

Not sure of your tank/cylinder setup, but pumped hot water does require a reservoir of cold water to replenish the hot cylinder as it is used.

I have no experience of fitting a pump to a combination cylinder, and suspect that it runs a greater risk of the pump running dry due to the small volume header tank which feeds the hot part of the cylinder. It all depends on the size, the rate at which it is refilled and the flow through the shower.
Hopefully one of the pros will comment before you get stuck in.