shower pump for instant water heater

[derekcfoley]

My bathroom shower is directly mains fed via an instantaneous water heater, my pressure is 3bar on the mains and 20 litres per minute in terms of flow rate. I've fitted a nice bathstore Cloud 500 huge shower head and plan on adding 4 shower jets around the shower area. The jets are seperately controlled from a flow valve, so can be controlled seperately from the flow to the shower head.

My problem is this - As I'm using an instantaneous water heater, at the moment the flow to the shower head has to be turned down to a "dribble" virtually to get decent heat for a shower. So my thinking is this: fit a shower pump, hopefully as quiet as possible to increase the performance, as well as a second instantaneous water heater in series to solve the reduction in flow required for a decent temperature.

My 2 questions are as follows - can anyone help?
1) I'm finding shower pump selection tricky - I've seen lots of pumps online but little in terms of how to select one based on the specs.
So I was wondering if anyone can enlighten me how a "1.5" or "1.0 bar" pump improve things - is it as simple as adding its rated value 1.5 or 1.0 bar respectively to the pressure coming out when its running - will this give me 4.5 and 4 bars of pressure on the outlets of the pump respectively?

2) If I'm putting in shower jets, should I be using a twin head pump? - I think this makes more sense - as obviously you might want each to be at a different flow rate. With these twin head pumps - does each end of the pump start up independently if only the shower is turned on and not the jets?

3) I keep reading that shower pumps should not be connected directly to the mains, but in my situation it is obviously mains fed as I have no tank - so both the hot and cold come through directly from the mains "on demand". Theoretically there is no issue of contamination anyway - is this a warning for people connecting hot tank fed water and mains cold supply through the pump?.

4) Anyone recommend a really quiet shower pump? My home has a flat roof and is timber construction, so the quieter the better obviously!

Thanks in advance for your help!

 

[seco services]

as you have already said you have read that you can't fit a pump to mains water supply.

this is correct it's illegal to fit a pump of the size you need direct to the water main pumping the volume you want.

your idea won't work anyway.

 

[derekcfoley]

Hi seco services - thanks for the reply -

Surely the reason for the bye-law issue of contamination is due to mixing stored (hot tank water) and cold mains water together directly though one unit, my system doesn't do that its all directly mains fed. Remember its not a conventional stored water system at all.

When you say "your idea won't work anyway" can you explain why specifically please - that would be useful to help me decide the best approach.

Thanks!

 

[bengasman]

3) I keep reading that shower pumps should not be connected directly to the mains...

If you keep reading that you can not stick a pump on the mains, why do you ask what pump you should use for the mains?
The answer is simple: no, you can not stick a pump on the mains.
Your problems is not with the mains pressure anyway, it is a matter of faulty design.

 

[seco services]

direct mains water its illegal to fit a pump to if the pump will draw more than 12 litres per min.

drawing water from the main supply by pump can draw more water than the main supply can provide and cause a vacuum condition so creating conditions in which backflow can happen.

you can't put two instantaneous water heaters in line.

 

[derekcfoley]

bengasman - I want to understand the reasons behind the laws on it thats all. Additionally most people's water systems in their homes in the UK are not the same as mine, I have no room for a tank and a flat roof - and being in a remote area there is no gas so a combi is out of the question, and I don't really want to go LPG as I want to keep everything electric so I can eventually follow the solar / wind microgeneration route for power to offset it all in the long term. So my situation is not standard.

Basically I just want to understand all the aspects and understand all the issues, which is why I posted here before making any decisions on how to improve it - so I appreciate any comments as its all useful knowledge that helps me build understanding.

Seco - Thanks for the useful info re the water draw issue... ok so I need to make sure whatever I use (if I do it) doesn't draw a ridiculous amount - that makes total sense - brilliant - all I need to do now is work out what the theoretical flow rate will be

Re the backflow issue, hmm - this is making me wonder whether I really should fit a non-return valve on the mains inlet after my stopcock to make sure this never ever happens?

Re the inline solution using 2 heaters, my Redring Powerstream heater doesn't actually reduce the flow pressure much as it goes around a single pipe loop with an element around the pipe, so the inbound pressure is virtually the same as the incoming supply, which is part of the reason why its so poor at full flow. In fact you only get a decent temperature by turning the shower/basin valve right down flow wise (Its fine on the sink obviously as less flow is required).

So at the moment it basically elevates the water temperature from the incoming mains water temp at full flow through the unit to approx 25 degrees from about 6 degrees from the incoming cold mains pipe - so if the cumulative increase in water temp is 19 degrees with one instantaneous heater running at full flow through the unit is 14 degrees, then I can't see why wouldn't a second one unit connected in series would bring it up another 19 degrees without compromising flow rate as I do currently - resulting in approx 44 degrees. The unit is triggered by 0.5 bar minimum flow rate - so no issues there really.

I know its unlikely that anyone's rigged up such an unusual system - but I'm limited in options in my home. I guess its more like something you'd see in Spain or the continent probably!

 

[derekcfoley]

Thanks for all the info chaps..

Re flow rate.. Sorry - Its not 20 litres a minute that the shower produces actually, sorry I misinformed on that.

What I meant was that looks like the theoretical maximum of the supply looks like it is this - with a tap on the end of the pipe that feeds the water to the valve - it fills a 2 litre container in 10 seconds when opened up fully - so 2 x 6 = 12 litres a minute by my calculations.

So I think theoretically would be the absolute maximum the supply could feed to the pump.

My reason for asking originally about this is how do you work out if a shower pump's rated bar spec will work with incoming flow rate / pressure? As I guess otherwise it will cavitate as seco mentioned.

I'm guessing there is also no "speed control" on the pump to turn it down, so supposedly the bar rating is the essential bit, as otherwise its too powerful and causes those problems.

Also how do I calculate what theoretical water pressure I need for an "envigorating power shower style flow" - e.g. 4 jet nozzles and the big shower head?

 

[bengasman]

bengasman - I want to understand the reasons behind the laws on it thats all.

Do a course to get a nvq, your knowledge is far too limited to understand any explanation.
Bottom line is: the powers that be have decided you are not allowed to do it. End of.

 

[derekcfoley]

bengasman... I'm doing my own bathroom, I'm not a plumber - and I don't want to make a career out of it, or start training for months just to fit one thing that could be done in a day - and never use the knowledge again - that seems a bit daft.

I enjoy learning and doing things myself - The whole point of the internet is sharing help and knowledge - Would you really want to go on a course for years just for one bathroom project? No. Compared to the point of this forum - so someone can just reply with a few useful helpful postings and guide me in the right direction.

So please be more considerate and try and be constructive in your criticisms - otherwise whats the point in posting on a public forum asking for advice and technical help from others with more knowledge. If I knew what I was doing I wouldn't be posting!

Perhaps I shouldn't be using this forum if people assume posters are experts in the field - I'm not - I just want some technical advice from more experienced people!

Thanks to everyone else so far with their useful contributions, Its all helping chaps - cheers!

 

[bengasman]

Your questions are pointless. When legislation forbids to do something, there is no point for an amateur to try to understand why that legislation has been made that way. Did you ask your driving instructor to justify the need for a driving license?

 

[derekcfoley]

Ignoring you Bengasman, you're not being helpful.

 

[slapper]

bengasman... I'm doing my own bathroom, I'm not a plumber - and I don't want to make a career out of it, or start training for months just to fit one thing that could be done in a day - and never use the knowledge again - that seems a bit daft.

I enjoy learning and doing things myself - The whole point of the internet is sharing help and knowledge - Would you really want to go on a course for years just for one bathroom project? No. Compared to the point of this forum - so someone can just reply with a few useful helpful postings and guide me in the right direction.

So please be more considerate and try and be constructive in your criticisms - otherwise whats the point in posting on a public forum asking for advice and technical help from others with more knowledge. If I knew what I was doing I wouldn't be posting!

Perhaps I shouldn't be using this forum if people assume posters are experts in the field - I'm not - I just want some technical advice from more experienced people!

Thanks to everyone else so far with their useful contributions, Its all
helping chaps - cheers!

Well done Derek,if you dont ask then you wont know. Some people on here think theyre above reproach

 

[bengasman]

Say one troll to another:" how long are you staying?"
"until I get pizzed off." replies the other one.

Sorry guys, my mistake; that was 2 pubes on a bogseat.
Easy to get them mixed up.

 

[Hugh Jaleak]

IMHO the reason behind the byelaw is to prevent contamination of the public water supply. The byelaws cover the installation of water supplies in buildings and incorporate a number of aspects where checkvalves, air breaks etc must be incorporated to ensure backflow is prevented.

Should a negative pressure occur on the water supply, possibly a burst main as an example then theoretically water could be drawn back into the public supply. If a garden hose was filling a fishpond then water from the pond, or a shower hose left in a bath full of water, then this water could be siphoned back into the mains thus contaminating the supply.

Plumbers dont write the byelaws, but they are duty bound to carry out installations that comply. Hence your idea is not allowed. Even if it was legal to install I doubt it would work, you would be trying to draw more water than the supply can provide, and the pump would cavitate. I think these showers need a large capacity of stored water to work properly, the mains supply alone is never going to be sufficient.

 

[Steady]

Degsy old son- you can't pump the mains pressure supply as has been said already.
What you think you're going to achieve by doing so I haven't a clue.
You won't get an improved showering experience at any rate.
If you don't like the advice I'm afraid that's hard luck.

I would try restricting the cold inlet to the shower and see if that helps.