choosing the right shower pump

neilb32

can anyone help so confused , i live in a detached house bout 14 years old
the hotwater upstairs is gravity fed and cold water is mains,( i have a hot water storage tank on the landing) the hot water pressure in the upstairs bathrooms isnt great and iam fitting a mixer shower in the ensuite so iam after a pump that will boost the hotwater for the shower mixer and also the hotwater taps in the main bathroom , i have rang stuart turner who recommended there monsoon universal 3.0 bar pump and salamander said i need there esp80cpv 2.4 bar, which do i choose, would these be to powerfull and would it drain my hotwater tank too fast, there are only 3 of us in the house and odds are we wouldnt be using both bathrooms at the same time, iam so confused which pump would you guys recommend.

peterbaker

I hope I don't confuse you further, because I am not an expert but here goes ...

Been there and come out ok the other side, Neil, so don't fear

I should however repeat that I am no plumbing expert ... I am sure one or two of those will be answering later when they've had their dinner . Meantime let me tell you what this novice DIYer found out earlier this year ...

For five years I had happily made do with a cheap electric cold mains only fed shower unit as fitted when my place was new at about the same time yours was built.

Then the water company reduced the pressure in the road so low that the safety cut-out on my shower unit switched off the water heater. So I had to consider what to replace it with. I settled on a decent mixer unit mounted on the bath taps. Then my problem was not the low cold water pressure but the even lower hot pressure.

I definitely needed a pump because my hot water system is gravity fed from the tiniest cold water storage tank you can imagine which is mounted only at shower head height so zero pressure right where I needed it!

Your landing hot water tank may however be fed from a cold-water storage tank higher up in the loft in which case you are definitely out of negative head territory, and so I think all you really need to worry about is getting a hot pump pressure that is within 0.5 bar of the mains cold pressure so your mixer can balance the two.

Stuart Turner make exceptionally good pumps but I did find that in my case when I spoke to their Technical Dept. they pushed their negative head version of the Monsoon when I didn't need to spend that much. I gambled that at the level of the bath tap mixer (where I knew the hot water was already able to flow adequately to get into the bath) it should be enough to start the pump before I pulled the diverter knob to get the water up to the shower. I was right. I didn't need negative head and that did indeed save me around £150 if I recall correctly. I bought the cheapest lowest pressure positive head pump from a Stuart Turner dealer on the web for £130 including postage and am very happy with it.

In my case I only have one bathroom so that made my choice slightly easier. Mine is a 2 bar (max) single pump which pumps the hot water only. The mains pressure in my flat is also quite low (no more than 1.5 bar at shower head)

The thermostatic cartridge in the mixer units can typically handle an imbalance in hot/cold pressure of about 0.5 bar, and so mine handles it just fine without belting out too high a pressure that might have risked draining my tiny cold-water storage/header tank.

You mention lowish hot water pressure and draining the tank - are you sure the ball-valve in your cold water storage tank hasn't become gummed up with calcium? Does the cold water storage tank run dry when you run a bath for example (it shouldn't). The flow from the mains via the ball valve should be able to keep up with the flow out to the hot water cylinder when you are using hot water. If the cold water storage tank runs dry then that will reduce the available pressure head to the hot water cylinder and your hot bath tap will start off ok but then be seen to start running slow - is that what you have seen?

If so, you might first wish to fix the ball valve.

Are the pump companies suggesting a single or a double (i.e. both hot and cold) pump? Not all single pumps can withstand hot water although I think all recent Stuart Turner ones are ok.

neilb32

the pump companys are pushing a single pump but the one,s that do both negative and positive pressure, so do i only need a positive pump if my cold water storage tank is in the loft above the hot water tank on the landing, also the subject of my tank running dry i meant my hot water tank as i though a 3.0 bar pump would empty it in no time, to be honest i dont want power shower flow rate just a normal rate for my mixer show and my bath taps,

peterbaker

Yeah sounds like they were pushing the negative head one on you too Neil ! I guess we can't blame them too much because that way they get fewer complaints from people whose pressure might be on the (low) limit at the shower head.

In a simple gravity fed system like mine (and yours I think) your hot water pressure is governed by the level in the COLD-water storage tank that feeds the hot cylinder, not by the height of the hot water cylinder. So I can't see how you would really need negative head (experts may be able to give us a different angle...)

Also you don't necessarily have to worry about a higher pressure pump using too much water as you can turn down the flow at the shower, can't you . The volume of water used is a factor of flow not pressure.

The amount of hot water used will also be limited by the demand for hot water at the thermostatic cartridge in the mixer unit i.e. irrespective of your pump pressure it won't use any more than is needed to balance a corresponding volume of cold mains water to achieve the temperature you set.

I think therefore the main thing you have to worry about is getting a hot single impeller pump that has a pressure rating within 0.5 bar of your cold mains pressure. (This assumes you are 100% certain that the cold side on both your bath mixer and your ensuite mixer are mains fed i.e. not gravity fed from the cold water storage tank in the loft).

Question is, what's your cold mains pressure likely to be at the mixers? Obviously on the first floor it would be perhaps 0.25 - 0.35 bar lower than it is in the road, but do you have any idea whether its a high pressure main that you are on, or a low one?

If you buy a 2 bar pump and the mains pressure turns out to be 3 or 4 bar then you may have an annoying imbalance problem in your mixer thermostat with a constant pulsing affect which may be bad enough to keep stopping and starting the pump which apart from being annoying is probably very bad for the pump.

neilb32

peter thanks very much they are very good responses and lots of info, i definatly know my bath and mixer are mains pressure i have had it checked, the mains pressure in the house even upstars is very good so iam thinking maybe the 3 bar may be a safe bet

peterbaker

Before you commit Neil, might be interesting to see if any real plumbers might comment ...

I see that it is not only the negative head pumps that are expensive, but also some of the higher pressure ones.

Mine was the top one on this page: http://www.plumbworld.co.uk/stuart-turner-shower-pumps-2388-0000 which arrived in a box which said 2.0 bar on the outside (and also on the rating plate IIRC). I at first thought they'd sent the wrong one but elsewhere I established that the pressure can be stated as a maximum or some lower (possibly constant flow?) pressure. Either way, mine works just fine with my <=1.5bar mains.

The one you want might be the fourth or fifth one down the page and I wouldn't be surprised if the Stuart Turner box (and the rating plate) says 3.0 bar and 4.5 bar respectively. Have a look at the Stuart Turner website on http://www.stuart-turner.co.uk/products/monsoon ... Having seen and ordered the real thing from Plumb World, it looks to me like Stuart Turner simply describe them using the maximum pressures they can deliver rather than the way Plumb World describes the same units.

Here's another money saving tip I'll share and one I'd also be interested to hear a comment upon from the experts ...

I fitted my pump myself, in the space under the bath. The ceiling isolater switched electrical connection was already there for the old electric shower so I didn't need an electrician for that.

Having noticed the tap fitting and the fitting on the pump exactly matched the fittings on typical washing machine/dishwasher pipes, I decided to save £££s by using a red one (suitably stamped and rated for the hot water and pump pressure) to connect the pump to the hot side of the mixer. It cost me just £5 in B&Q .

keystone

neilb32 wrote: »

can anyone help so confused , i live in a detached house bout 14 years old
the hotwater upstairs is gravity fed and cold water is mains,( i have a hot water storage tank on the landing)

Is your HW cylinder fed from a Cold Water Storage Tank in the roof? Are you sure all your cold water is mains? Simple test - turn off the cold mains at your stopcock. Turn on kitchen tap - does it still run? Go to bathroom operate cold tap on bath. Does it still run?

What is the capacity of your HW Cylinder and what is the capacity of the CWST if you have one?

Stuart Turner are good - so are Techflow. Techflow maybe a tad expensive for you but I really like them.

Cheers

keystone

peterbaker wrote: »

Then the water company reduced the pressure in the road so low

Thats the problem with trying to balance mains cold with pumped hot they can do it again or raise it at their whim. It may have worked for you but its far from an optimal system design.

Cheers

keystone

peterbaker wrote: »

So I can't see how you would really need negative head (experts may be able to give us a different angle...)

Neither can I. I can put a shower pump in the roofspace near the CWST and still not need a neg head version.

Cheers

Canucklehead

Hi,


Have had no need to fit a pump for hot only and would have thought it would be discouraged by water companies.
No so according to Salamander.

Personally I wouldn't consider doing this at all, too much fiddling about with check valves and possible problems with balancing it.


I would fit a 50 g CWSC. run an independant cold and hot feed to a twin impeller pump then to a shower.
If you really want it to do a bath as well then tee off the shower supply.

I would avoid pumping the whole bathroom as flushing the toilet in the middle of the night will fire the pump.


GSR

moonrakerz

keystone wrote: »

What is the capacity of your HW Cylinder and what is the capacity of the CWST if you have one?

Stuart Turner are good - so are Techflow. Techflow maybe a tad expensive for you but I really like them.

Good point raised here; if you install a really powerful pump you will very rapidly empty your hot water storage tank. If you are looking forwards to having long sessions under the shower you may need to factor in a new tank - if you have room. Check the flow rate of the pump before you buy.

I have a Techflow pump - very good.