quick shower pump question!!

[dynomo]

Hi chaps,
was asked to look at a faulty shower pump today, havn't really installed one myself so was a little confused. Pump was leaking from the main body and making a loud grunting sound.
this is the pump:

pump feeds a manual mixer shower. Hot water tank inside a storage room adjacent to the bathroom 1m above ground level, pump sits under the bath tub approximately 2m away from the hot water tank, direct hot water feed into one inlet of pump and cold mains pressure through the other inlet!!! I advised the chap that when he did the install, he wasn't meant to connect mains cold to the pump!!

Question is, can I connect the cold water feed direct to the shower and have just the hot water pumped?? This will mean that one side of the pump will have no connections, is this ok? It will mean equal pressures at the shower which is ideal.
Dan!!! Help....
cheers

 

[GeckoGas-com]

You won't actually get equal pressures if one is pumped and one is mains...

Ideally you'd want to run a seperate supply of cold from the tank to the pump. This would be my advice to the client anyway.

 

[dynomo]

thanks for the reply
there is no cold water tank, all cold feeds are mains pressure.
ive read through some old posts here and some gentlemen have suggested 2 x hot water pump inputs in parallel with the outputs combined to feed the hot inlet at the mixer valve, along with a pressure equalising valve after the pump. Im not sure which is the best method. To go out and buy a single impeller pump is not an option I'm afraid...

 

[Dan Robinson]

So let me get this straight?

Your customer has mains cold water running through one side of a twin pump; the hot water is from a gravity fed cylinder sucked through the other side of the pump.

And you are asking a DIY forum for advise?


You said there is no "cold water tank"; how is the cylinder filled?

 

[dynomo]

Hi Dan, I'm a little sketchy on gravity fed systems!! You'll have to bare with me as I am still undergoing the learning process.
customer is infact a chap who lives a few doors away, just wanting advice.
He doesn't want additional pipes entering the bathroom etc etc, just wants all the work to be carried out under the tub which is fair to say.

Is there a solution mate??

 

[Dan Robinson]

Sorry, got a little sozzled last night after a 5 hour drive...

You really need to suss out if this is a system with gravity hot and cold, or mixed; AND whether or not this pump is trying to handle mains.

If the latter then the guy HAS to either change the pump for a single head one and pump the hot. Or as Gecko mentioned run a separate cold feed from the storage tank.

 

[dynomo]

all that is visible to the naked eye is a black hot water tank in the storage room!!
this has a ball valve system up top and it clearly states this on the tank itself. It sits 1m from the ground, to it we have cold mains pressure supply coming from downstairs. From it, everything else is then fed, i.e. heating flow and return, hot water to taps etc. The property is a 2 floor flat so there cannot be any additional cold water tanks up above as this would just not be possible. I hate gravity systems, the confuse the hell outttta me!! Oh and there is a boiler hooked up in the kitchen downstairs, prob not a combi, looks like an ordinary one.
As said previously, a single impellor pump is not an option so too the idea of running additional pipes.

If I were to connect 2 x hot into the pump and have them both exit into hot side of the shower, and have cold directly to the shower, would this not work!!!

 

[GeckoGas-com]

You are really going to need to be more descript about the type of system this guy has installed...

all that is visible to the naked eye is a black hot water tank in the storage room!!

a) Black? Painted black, black plastic or it was simply dark in there?
b) Hot water tank as in the water in it was hot, or this is the cold storage tank that supplies the hot water, or is the the feed and expansion tank for the central heating?

From it, everything else is then fed, i.e. heating flow and return, hot water to taps

Are you sure everything? If so; this is not a normal tank and could be an Elson tank or a SystemMate - Or; hate to say this - From the description of this black "tank" - a combi!

Oh and there is a boiler hooked up in the kitchen downstairs, prob not a combi, looks like an ordinary one

Errrm... Think about it logically; is it a combi if it has a gravity cylinder?

As said previously, a single impellor pump is not an option so too the idea of running additional pipes.

Well if that is the case; tell the guy to bodge it himself and walkaway from the job IMO.

If I were to connect 2 x hot into the pump and have them both exit into hot side of the shower, and have cold directly to the shower, would this not work!!!

It will work; but it's a bodge; you'll also need to fit non-return valves everywhere as you won't be able to trust the ones in the shower and don't expect the shower to be able to mix perfectly as the supplies won't be balanced.... But yes; in short; it will work.... Just bodged.

 

[dynomo]

thanks gecko
all the bloke wants is a working system
im going over later tonight and will inspect the storage cupboard alot further!!!
so where exactly would the non return valves be placed??
im assuming prior to connections at the mixer valve?? and possibly before the mixer??

 

[GeckoGas-com]

You'll need them on the outlet of the pump before the shower mixer.

 

[Chrismac]

I take it its one of these cylinders http://www.plumbingpages.com/featurepages/HWcombination.cfm if I have read your description correctly?

 

[Softus]

Pump was leaking from the main body and making a loud grunting sound.

Replace it.

hot water feed into one inlet of pump and cold mains pressure through the other inlet!!! I advised the chap that when he did the install, he wasn't meant to connect mains cold to the pump!!

Correct.

Question is, can I connect the cold water feed direct to the shower and have just the hot water pumped?

Yes. Get a single impeller pump for the hot side, and connect what used to be cold pump inlet to a pressure limiting device. Connect the output of the PLD to the cold inlet for the shower. Adjust the PLD to match the claimed pump output, e.g. 1.5 bar, or 2.0 bar, or whatever.

 

[dynomo]

thanks softus
the only issue is that he can't replace the pump, supplier will only do him an exchange so along with cost issues and stuff, he is stuck with a new c50 pump as above...
i think i will go with gecko's advice and give it a shot
what do u think softus, i know ur a man with serious knowledge on plumbing!!!

 

[Softus]

Oh thanks. Why not just clamp me in a set of stocks with a tub of overripe tomatoes nearby?

If the customer can't/won't change the pump, then, leaving aside the leak problem, I would treat it as a single impeller by connecting the hot service to both inlets and both outlets to the shower hot inlet.

To discourage cavitation I'd use 22mm to both pump inlets.

You still need to balance the shower feeds though, so as before with the PLD. An alternative to the PLD is a pressure balancing valve, which is a better solution but marginally more expensive.

 

[dynomo]

cheers softus
you're a credit to this forum mate