Shower pump specs

Hi all, first time to post on here, looking for some help from knowledgeable/experienced people here.

We're installing an ensuite and I'm looking at my options to get a decent shower. The shower head I want uses approx 15 - 18 l/min at 3bar. The shower head will be fitted to the ceiling. The CWS is in the loft but is only a joist height above the ceiling, hence a negative head pump looks necessary.

I've loked at pumps - looks like Stuart Turner monsoon is the best to go for, just wondering what pressure I should opt for, there are 1.5, 2, 3 and 4, bar options. What difference does this make - is it simply the flow rate they can kick out or does it need to match the shower head? I was going to go for the 3 bar option as the shower head specs say 15 - 18 l/min at 3 bar which is enough.

I've also researched conenctions for the pump. I'm happy about connecting the CWS from the tank in the loft. The hot water tank has a blanked off connection on the side, which looks like a 22mm threaded connection, just below the weld at the top. Can I use this as the hot water feed to the pump? Also what else should I be fitting, i.e. to remove air etc etc?

Final question/concern - the flow rate into the house is roughly 18 l/min at the kitchen cold tap. If the pump is using that is there a risk of draining the tanks and damaging the pump, or will the pump shut off if water level drops? We will need to be able to use 2 showers at once as well so surely the tanks will drain faster then they can fill?

Many thanks in advance for any responses.
Harve

Blimey... busy forum! Anyone able to advise / help? Cheers

Harve said:

Blimey... busy forum! Anyone able to advise / help? Cheers

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Have patience, we don’t get paid for this ya know!

Harve said:

The shower head I want uses approx 15 - 18 l/min at 3bar. The shower head will be fitted to the ceiling. The CWS is in the loft but is only a joist height above the ceiling, hence a negative head pump looks necessary.

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Almost certainly.

Harve said:

I've loked at pumps - looks like Stuart Turner monsoon is the best to go for, just wondering what pressure I should opt for, there are 1.5, 2, 3 and 4, bar options. What difference does this make - is it simply the flow rate they can kick out or does it need to match the shower head? I was going to go for the 3 bar option as the shower head specs say 15 - 18 l/min at 3 bar which is enough.

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My preferred pump is the ST; I would never use less than 2 bar in any situation. 15-18l/min @ 3 bar is some shower head but if that’s what it requires then that’s the minimum you should use. If you look at the manufacturers flow/pressure chart for each pump you will see there is a correlation between flow, pressure & pipe size. You should, however, consider that having a very high output shower will require significant cold & hot water storage capacity. The commonly sized 250/150 litre cold/hot water tanks fitted in the majority of properties will not be sufficient for such a high flow rate & you will need to seriously upsize both; do the math, you will find you will be limited to very short showers! If you have similar sized tanks, I would not advise you go any higher than around 12 litres/min, either that or be prepared to replace/upsize both which aint gonna be chaep.

Harve said:

I've also researched conenctions for the pump. I'm happy about connecting the CWS from the tank in the loft. The hot water tank has a blanked off connection on the side, which looks like a 22mm threaded connection, just below the weld at the top. Can I use this as the hot water feed to the pump? Also what else should I be fitting, i.e. to remove air etc etc?

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Difficult to say what it is without seeing it & knowing more about your heating system. Even if it is spare, you can’t just tap into it unless it’s an Essex flange or you will draw air through the pump & ruin it in a very short time. Along with most pump manufacturers, I prefer the Essex full flow flange rather a dual purpose top flange which may not cope with the sort of flow rate you’re looking at anyway. It’s also important the supply & delivery pipe work & tank connections are correctly designed & have as few restrictions as possible; full bore isolation valves only, bends rather than elbows & runs as short as possible. We haven’t had many pump questions of late but if you search back though the archive posts you will find many that should answer most of the questions you may have; if not post back.

Harve said:

Final question/concern - the flow rate into the house is roughly 18 l/min at the kitchen cold tap. If the pump is using that is there a risk of draining the tanks and damaging the pump, or will the pump shut off if water level drops? We will need to be able to use 2 showers at once as well so surely the tanks will drain faster then they can fill?

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You’re starting to see the relevance, see my comments on flow rate above. You will never be able to use 2 showers with that flow rate simultaneously without a tank the size of a water tower; & that’s just the cold, remember it also has to replenish the HWC! At those rates, you should fit a low water cut out switch in the CWS tank.

Many thanks for the response Richard, sorry if I was a bit impatient, was worried that it’d be missed so far down the listings already.

Yeah I see the concerns. However I’ve been doing some maths –

If the new shower head uses 18l/min (manufacturer says 16.5, but another site said 18 so I’ll take 18 to be conservative), the existing head in main bathroom I’m not sure about but lets assume 10 l/min (its a conventional mira unit on the wall).

So in total we’ll be using 28l/min with both showers running.

Assuming 2/3rds hot vs 1/3rd cold to showers then we’ll need 19 l/min hot water (2/3 *28). Therefore a 150 liter HWC will last for just under 8 minutes. After that it’ll run cold. So if both showers are turned on at same time we’ll have 8 minutes each.

Assuming (at worst) we get 16 l/min mains supply to house then we’ll be using 12 l/min more than can be replenished (28 – 16). If we have 400 liters total storage capacity in the house then we’ll have enough to run both showers for over 30 minutes before we run out of water completely. 22 minutes of which will be with cold showers

An 8 minute shower seems enough, we only use 2 showers at once while getting ready for work in the mornings so we wont be hanging around. Should have mentioned that the ensuite will have 2 shower heads, which cant be used at the same time. The smaller head will normally be used and the larger head (the one I’m worried about) will be used occasionally so will probably be quite rare to have the worst case as described above happen.

If we’re using 19 l/min of hot though, will the hot tank be replenished at more than 19 l/min or is there a danger of that running dry? Its a great shower head, so I really don’t want to downgrade as it’ll be awesome, its a hansgrohe raindance 240, as the builder said – we’d be able to invite our friends round to join in (not that we will mind!).

Thanks

Harve said:

So in total we’ll be using 28l/min with both showers running.
Assuming 2/3rds hot vs 1/3rd cold to showers then we’ll need 19 l/min hot water (2/3 *28). Therefore a 150 liter HWC will last for just under 8 minutes. After that it’ll run cold. So if both showers are turned on at same time we’ll have 8 minutes each. Assuming (at worst) we get 16 l/min mains supply to house then we’ll be using 12 l/min more than can be replenished (28 – 16). If we have 400 liters total storage capacity in the house then we’ll have enough to run both showers for over 30 minutes before we run out of water completely. 22 minutes of which will be with cold showers

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Assuming your using a capacity of 250 litres for the CWS tank, that’s the capacity which will restrict your maximum available shower time (hot or cold) 250/12 = 20 mins not 400/12 = 30 mins! I’ve never checked a tank but my guess is that the published capacity is the theoretical maximum & not the useable capacity; the CW feed will not come from the bottom of the tank to avoid drawing off sediment so you’ll be loosing some capacity there & a float switch by its very design means it must be mounted 100mm above the outlet so the pump will be shutting off long before it reaches that level, which could reduce the useable storage capacity by 20-25%!

Similarly, a 150 litre HW storage cylinder will not actually contain 150 litres of useable hot water @ 60 degrees. Heat rises so although the top of the cylinder will be hotter, the temperature will reduce the further down the tank you go to the point where the stat is mounted (usually 1/3 from bottom). Below that it will be less than 60 degrees & once you go below the input tapping for the internal heating coil, it won’t be very hot at all. Depends on the tank I suppose but looking at mine, I reckon these two factors could reduce the useable HW capacity at by 10 -15%; there may be a recognised method of calculating the useable capacity, I’ve no idea.

Harve said:

An 8 minute shower seems enough, we only use 2 showers at once while getting ready for work in the mornings so we wont be hanging around. Should have mentioned that the ensuite will have 2 shower heads, which cant be used at the same time. The smaller head will normally be used and the larger head (the one I’m worried about) will be used occasionally so will probably be quite rare to have the worst case as described above happen.

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8 minutes is more than enough for me but the biggest inconvenience comes when you want to use showers simultaneously when you have a few guests staying as I often do. I have around 250 litres of HW storage (a 100 litre in the loft attached to solar panels) when both my daughters & their partners stay we usually all just about manage a decent shower but I then have to boost the HW as there is none left. if we don’t all get in before one person in particular, he uses so much HW that someone’s going to get caught out; it’s difficult to tell your guests “you can only shower for 3 minutes”.

Harve said:

If we’re using 19 l/min of hot though, will the hot tank be replenished at more than 19 l/min or is there a danger of that running dry?

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Not of the hot running dry; it will be restricted by the flow rate from the CWS tank this in turn will restrict the max pump delivery rate; the cold water pumped rate will be restricted in much the same way; the pump cannot push out more then it can suck in which is why direct & unrestricted delivery lines to the pump in 22mm are important.

The CWS tank will be your problem as it’s unlikely to replenish the CWS tank at that rate & so will gradually fall, hence the need for a low water level cut out switch; you can do a simple test by tying up the ball valve & emptying ½ the tank, get a suitably sized container ready (say 5 litres), release the ball valve & time how long it takes to fill it, then it’s simple math again.

You have the intelligence to understand what’s going on, it’s for you to decide really; but the practical side of things has a habit of never quiet matching the cold mathematical theory.

Harve - be very careful about the exact shower spec.
Have you eg got this one? (the ECO one)
http://www.hansgrohe.co.uk/uk_en/110483_32313438355F32355F3635313537.htm

and do you understand pump curves?

This
http://www.stuart-turner.co.uk/media/5201-Performance-Monsoon-Standard-4.0-bar-Twin.pdf

shows that a 4 bar pump will give you 18l/min at 3 bar.

You wouldn't actually get that flow, because of losses in the pipework & valves. If you use something like a HG Ibox with diverter valve, it'll knock it right back..

The one I was looking at was this:

http://www.hansgrohe.co.uk/uk_en/110483_32313438355F32355F3633323939.htm

with this:

http://www.hansgrohe.co.uk/uk_en/110411_32313532365F32355F3632303837.htm

I kinda understand pump curves, I see your taking a 30m head - is that a standard for shower pumps with mixers etc?

The pump will be about 2.5 meters below shower head, its the other side of the house from en suite so will have to go through about 15m of 22mm pipe and then through the ibox to shower head. Is a 30m head adequate to get about 18l/min to the shower head? Seems like 4 bar pump is required then? More expense but as long as its worth it afterwards!

Never thought specing out a shower pump would be so complicated! Cheers for the help guys!

30m head = 3 bar, it's just another way of looking at it. If you look at the pump curves you'll see that the 3.0 bar pump delivers 30m head (3.0 bar) at zero flow, IE this is largely theoretical. I've kind of lost track in all this of what flow rate you want and whether you're also pumping the cold or not, but a ST Monsoon Universal 3.0 bar Single will only give you 1.0 bar at 18l/min, as will a STMU 3.0 Double at 28l/min (the total figure you've estimated you need for hot and cold combined with two showers running).

If you're pumping the hot only and really do want a maintained 3.0bar at 18l/min (that's quite a lot!) then even the 4.5 bar won't keep up, you need a Monsoon Extra 3.5 bar Single for that (or a Salamander ESP120CPV). If you're pumping the cold as well and need 28l/min total output (AFAIK the output quoted is total and not from either side) then you need a pair of Monsoon Extra 3.5s, or the Salamander ESP140CPV Twin which will give you about 3.5bar at 28l/min total flow. If you can put up with 2.5bar then a Monsoon Universal 4.5 bar Twin will cut the mustard. Remember with all of these the aforementioned (by ChrisR) losses in the pipework and valves mean you won't actually get quite that much.

My recommendation, assuming you're pumping hot and cold and want at least 3.0 bar at 28l/min total is the Salamander ESP140CPV Twin. Slightly overspecced but better that than under. Best price on t'internet five minutes Googling has produced: £419.00 + £5.95 delivery http://www.bargainplumbing.co.uk/products/salamander-shower-pumps-esp-140-cpv-twin/70/ A pair of Monsoon Extra Universal 3.5 singles is nigh on £900, the Monsoon Universal 4.5 bar Twin £436, meaning that you're paying more for less performance with either of them

Thanks muggles,

I want to pump both hot and cold. The shower head is rated at 18 l/min at 3bar - I dont particularly mind if its slightly lower than this, but would like to be around 15 l/min at least. Will a ST monsoon universal 4 bar twin cope with that?

The pump wont have to supply to the existing shower in the main bathroom, I'm quite happy with that.

Also - there will be 2 shower heads in the ensuite - the large one at 18 l/min and a smaller one which I think is about 10 l/min. They cant be used at the same time. However if I'm specing up for the larger head then wont that overload the smaller head? or will the head restrict flow enough?.

Final question... sorry if a bit of a simple question...will the pump mind being used at half load sometimes, my wife likes to turn showers down when not washing her hair etc so will the pump be ok with not running at full load?

Ah, so I did misunderstand your requirements slightly then, the maximum required flow rate is 18l/min.

A STMU 4.0 Twin will give you 2.8bar at 18l/min, less pipework and valve losses which are almost impossible to calculate here. This is slightly less than your head is rated at, meaning your head will probably be giving out a bit less than 18l/min. It won't be a problem for your smaller head running at 10l/min provided it can cope with the pressure (check this with the manufacturers). At 10l/min the STMU 4.0 Twin will be giving 3.2bar.

Because of the way most pumps work they are always running at full load, all that changes is the flow rate / pressure, so your wife turning the shower down will be no more stressful on the pump than having a shower fitted to it that has a lower achievable flow rate to begin with.

Best price a quick Google has found is £409.95, free delivery. Not much cheaper than the much better performing Salamander ESP140CPV, but it does have five years' free warranty to they Sally's two years. Probably better rated for your needs as well, the ESP140CPV is overkill for one shower head (it'd be giving about 3.8 bar at 18l/min...might knock the kids over!!)

Brilliant that's exactly the answers I was looking for! Thanks all very much. Briliant forum this! Will save me lots of £'s!!!