power shower on cold mains??

Postby andy065 » Thu Mar 08, 2007 6:13 am

i live in a flat where the bottom of the cold water tank is a chest level - not much pressure there! Currently i have a power shower, but it struggles to suck the water through from the cold tank - hot is also thru a low level heated tank (cold from the mains sat in a tank and heated by hot water from the radiator system which is heated off site and pumped in).
My question is, what can i do to get good pressure??
I was thinking of getting rid of the cold tank and having mains supply to a power shower - could that work? i know it goes against 'current convention', but still...?
any help/advice gratefully received.
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Simply Build It

Postby simon_the_gas_man » Thu Mar 08, 2007 9:37 am

You could replace your cylinder with an unvented cylinder. This will give you mains pressure hot water all over your flat. We install these systems in many new developments, once you have one you will never do without it again. A good make is called a megaflow.

Hope this helps
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Postby Cpt Nemo » Thu Mar 08, 2007 5:19 pm

Hi Andy

A little confused by your mail - it's probably me!

If you are looking to get a shower with decent pressure, then you will need to supply both hot and cold water are roughly the same pressure.

A shower pump achieves this by taking cold water from the storage tank and hot water from the cylinder - boosting both to the same pressure and delivering to a mixer valve.

The cold main should be able to supply ample cold water, but then you need hot at the same pressure - which from the sound of it might be a problem!

The most logical option might be to have an electric shower installed - this will allow you keep your existing system for all the other hot & cold water taps. Electric showers are fed by mains pressure and the higher power ones (9 - 10KW) can deliver a good shower. However you will need to have the correct cabling, RCD etc installed by a qualified and Part-P compliant electrician.


PS You can find out more about our Weekend Plumbing courses by going to www.plumber-training.com/5.html
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Postby andy065 » Fri Mar 09, 2007 2:50 pm

guys - thankyou both.

If i get the hot pressure to match the cold mains (using an unvented cylinder as Simon suggests), can i then push both thru a power shower - i want the kind of shower pressure that pushes you against the wall and leaves bruises!
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Postby Cpt Nemo » Tue Mar 13, 2007 6:00 pm

Hi Andy

The simple answer to your question is yes, but!

1) You will need to make sure that the pressure is sufficient, in the option Simon mentioned the installer will (should) install a pressure reduction valve in the main line to ensure that the pressure in the system does not go above the threshold of the safety valve on the Megaflow. This would normally be around 2.75Bar, which would give you a jet wash!!!

2) If you have a LOT of demand on the hotwater side, you might get a great shower, but unless you put in a decent size Megalfow you could end up with short shower.

Have a word with a local installer and see what they recommend with regard to your Megaflow size - a bit difficult to do via this forum.

PS You can also find out more about the Weekend Plumbing courses by following the link at the bottom of each project on this site.
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Postby teach1376 » Tue Mar 13, 2007 10:08 pm

Shower pumps are not allowed to be connected directly to mains supply, besides they would do little to boost the supply if they were. Pumps push water through the system rather than suck and work best if sited as near as possible to the supply (cold water tank and hot water storage cistern). Have a look at your pump and see it's performance data, then check if you can get a more powerful pump as a direct replacement. A 4 bar twin impeller pump will supply enough water at a high enough pressure to satisfy any shower you care to build. You may need to increase the capacity of your Hot water cylinder because a decent pump, properly installed will empty it prety quickly
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Postby andy065 » Wed Mar 14, 2007 8:55 pm

ok, so would mains pressure (i can fill a 1 litre container in 4 seconds from the mains in the kitchen = 20litres/min flow) going thru an 8.5kw electric shower be greater than a '4 bar twin impeller pump' going thru, presumably, a simple mixer shower??
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Postby thedoctor » Fri Mar 16, 2007 2:01 pm

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Postby Andski » Thu Mar 22, 2007 10:55 am

For what reason can you not install the pump directly to the mains. Is it water board legislation? i.e. if you had a non-return valve before the pump would that be acceptable. Or is it that you could cause a drop in pressure elsewhere in the mains affecting your neighbours for example?
I suppose several people taking showers at the same time could cause a problem. Surely it's similar to a decent pressure washer on an outside tap?

Interested because someone I know is just about to start a power shower project.
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Postby julianroche » Tue Apr 24, 2007 9:00 am

Have installed Salamander twin impeller 'right' pump (1.5bar) to feed one shower. Has dedicated 22mm hot and cold feeds from cylinder and cold cistern. Pump feeds Aqualisa mixer and large ("deluge" type) shower head. Problem is pressure at shower head very disappointing. Is adequate by normal shower standards but not power shower perfomance which I was expecting. Makers advertise pump can feed 2 normal showers. Any suggerstions? Is pump not powerful enough?
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