Shower pumps - any dos and donts?

[A.Lee]

I'm fitting a shower pump for my parents, done them before for customers who have bought the parts themselves, but never bought one myself.

Single shower, so do I go for the single impeller to pump the hot water, and use the mains pressure cold?

Or, go for the double impeller to pump hot and cold, and add an extra feed from the header tank to feed the cold water side?

1.5 bar enough for one shower? Can an extra shower be added to the pipework, probably cannot be used at the same time, but I cannot see why one should not be fitted, so they have the pump supplying the main bathroom and en-suite.

Surrey flange - essential, or can I 'T' into the tank outlet?

What about thermostatic mixers - the cold will be a low flow at many times, do the pumps cope with the difference in flow between hot and cold?

Thanks Alan.

[Andy Cap]

I have no great experience but that is what I have done, taking an entirely new feed from the tank. Doing it this way, prevents other loads altering the cold pressure and it has worked well for many years.

Andy C

[David WE Roberts]

Our previous house - larger hot water cylinder (plumber fitted the shower pump to 'see how you go' and we emptied it pretty quickly) to replace the 'normal size' tank.

Large dual impeller pump - one feed from the cold tank in the loft and one from a Surrey (or similar county) flange at the top of the hot tank.

With this setup and 22mm pipework we could run two showers at the same time.

You do need a large header tank in the loft to avoid sucking it dry.

IMHO it is safer to have hot and cold at the same pressure from stored water - gets away from much of the variability with mains water pressure and allows you to pump more water than the incoming mains can supply in real time.

HTH

Dave R

[polygonum]

Similarly ours is fed from cold tank/hot cylinder precisely to moderate pressure differences - though our shower is a very modest one which wouldn't really qualify as a power shower - simply decently usable where the previous one was a dribble.

I did make sure that the downstairs WC was plumbed directly from mains partly to avoid that suddenly changing pressure. And the bathroom WC has its own direct-from-cold-tank 15mm feed. And other than the cold supply to the modest downstairs hand-basin, and hot-supply to the kitchen sink nothing else is going to dramatically or suddenly affect the available water pressure - and if the person in the bathroom chooses to turn the basin or bath taps - that is their look-out.

[Andrew Gabriel]

You need to take the cold from the tank too, from an outlet which is lower than the feed to the hot water cylinder, so that if the tank runs out for any reason, the hot stops first and the person in the shower doesn't get scalded.

There are fast acting shower mixers which include this protection instead, but they're expensive.

Yes.

Yes. You'll probably find you can use both at the same time.

Mine is T'ed into the cylinder outlet, without any apparent problems. It is T'ed in after the top pipe has dropped a good

2/3rds way down the side of the cylinder, and this might be to help ensure it doesn't suck air back down the expansion pipe (which it doesn't).

A thermostatic mixer is not essential in a stored water shower, and if you do have one, it can be one of the cheaper (slower) wax pellet types. If you happen to be going to France, identical shower mixers of this type are about 1/4 - 1/3 of the price there, compared with here.

A dual impeller pump will cope fine with flow in only one side. Mine has flow sensor switches in both sides, and either one switches it on. (Actually, it's one switch, with magnets in both sides.) If I'm heating water just for the shower, I only heat the hot water cylinder up to the right shower temperature, and then use the shower valve entirely on hot. (If legionnaires disease worries you and if your parents are elderly it probably should, this is not a good idea.)

[Roger Mills]

No, you need equal hot and cold pressure

Yes. And the cold feed to the shower should be below the cold feed to the cylinder so that, if the tank empties, the hot stops first [Having said that, mine are at the same level, and I've never had a problem]

Probably ok for a reasonable - rather than invigorating - shower.

Depends on geography. You'll need to take hot *and* cold from the pump to the second shower, when it might be easier to run a separate cold feed from the header

Probably not necessary with a 1.5bar pump. I've got two pumped showers, each with its own pump, and both effectively tee'd into the cylinder outlet, and they're both fine

Depends a bit on who else is using water at the same time. Both my showers have manual (non-thermostatic) mixing valves, and I've not had a problem. The temperature changes a bit when I adjust the flow rate - probably due to different resistances in the hot and cold feeds - but, in my case, it always goes colder if I reduce the flow - so no danger of scolding.

[newshound]

Double pump, Surry or similar flange. Get a Stuart Turner pump if you want it to last (will also be quieter than a shed basic)

[John Rumm]

That is the more normal arrangement. Worth checking that the main cistern can refill fast enough. Sometimes fitting a pair of fluidmaster type valves on the cistern can ensure it can keep up.

It will be significantly better than gravity alone. It might not satisfy those that crave the being pressure washed experience.

If the pipework is 22mm, then possibly. Most modern showers will give a decent enough experience on 7 or so lpm. I would fit a more powerful pump if doing two though.

I did a 1.8bar stuart turner pump on a normal hot water outlet and it was fine. That was with a nice easy and direct run from the cold cistern to the HW cylinder though.

You could also make up a warinx type flange using the existing outlet on the cylinder as an improvement measure on the normal one without needing to go as far as actually changing or adding a flange.

Yup - they allow "slip" as such - so blocking one side does not stall the pump.

[A.Lee]

Thanksto all for the input. I'll be going for a double impeller pump to feed both showers, run off a surrey flange (just in case!). Make of pump is unknown, price is a factor, so it may be a Grundfos or Salamander.

Thanks Alan.

[tony sayer]

FWIW ... recommend Stuart Turner Pumps:)...