Plumbing question - shower selection

[ntlreject]

Any Plumbers willing to advise before i buy?
I have to chose a shower for my aging inlaws living in a flat without a loft space. Combi hot water supply. I want to install a 800x1200 cubical and shower.
The cold water tank is practically level with the shower head position so I am thinking a pumped shower would work but is this right?

I checked Mira but they want 80mm minimum. Mira Elite.

Aqualisa told me negative head is ok with Quartz, Axis and Aquastream but the web site indicates you need head.

Electric heated ones are available with pumps but are they ok with Combi?

I need help -- Which particular shower is suitable to use with Combi, negative head, powered or electric please.

[SMHarman]

What do you mean by Combi? Combination boiler heating hot water on demand. Those don't usually have a cold water storage tank supply but are connected direct to the mains. With that kind of setup and two people living in a flat your best to use the hot water direct from the combi and mains pressure cold rather than anything electric. Much better pressure from the shower also.
You should then find out what this cold water tank is all about. By the time the plumber had finished working on installing my new combi boiler the cold water storage tank had been removed and my flat had an enormous new storage cupboard!

PS - not the advice of a plumber - just someone who has done this.

[ntlreject]

The hot water is supplied by a Combi boiler. there is a cold water storage tank for what ever reason, I guess because its in a flat.

[soup dragon]

i had a combi boiler, mira shower at my last house, no header tank, was feed direct from cold mains and combi boiler. Best shower i have ever owned imo!

[bw41101]

Reading this thread leads me to the conclusion that the combi could be of a very early design. Combi's have two separate systems combined within one unit - hence the name. One system is for domestic hot water and the other for central heating. The only thing I can think of is that the tank "may" be used to maintain the water level in the central heating circuit - but even then it's unusual.

As for the shower - you've (to my mind) two choices if you're using the combi to provide the water it must be of sufficient pressure. One way of checking this is to open the cold tap in the bathroom and watch the water flow - if it's strong then you should be okay to plumb in the shower.

If you go for an electric shower then (obviously) the pressure will have to be comensurate with that of the combi system (above) in addition an appropriate sized power cable will have to be installed to service same along with the isolation fittings and earthing arrangements.

One thing to be mindful whith the above types of arrangement is that if your in laws are sharing a building (flat) there's always the issue of others who may be using the water system at the same time. If this is likely, then any shower fittings utilising a combi system will have to be fitted with an anti scald device.

This wouldn't be an issue with an electric shower as they are designed to compensate accordingly for sudden changes in water pressure.

Hope this helps - good luck.

[ntlreject]

Thanks for that reply it certainly makes sense to me.. I may well take out the tank if the flow is good, the Combi is about 5 years old and as the Flats are association owned I can't do anything about that.
Shame on the association for not providing showers for the elderly who need them. They can no longer get out of a bath after one got in and being stuck for 2 hours.
18 months waiting - joke eh!

thankd again all.

[Vlad_Dracul]

Check the water pressure guage on the combi and tell us what the reading is? Is there any sign of a filling loop?

[ntlreject]

Hi All,
I have decided that this is going to be an electric shower not a pumped unit because the cold water tank is too small to cope with power shower flow anyway. Thanks for all the replies it did help a lot.
Cheers all

I am puzzled by the need for a cold water tank - a combi boiler system is usually effectively a sealed unit operating directly from the mains cold water & supplies the hot water at effectively the same pressure. This is why they work so well with mixer taps for running a shower & usually don't need a pump, but I only have experience of this in a first floor bathroom.

How many floors up is the flat?

[SMHarman]

Originally Posted by homealone

I am puzzled by the need for a cold water tank - a combi boiler system is usually effectively a sealed unit operating directly from the mains cold water & supplies the hot water at effectively the same pressure. This is why they work so well with mixer taps for running a shower & usually don't need a pump, but I only have experience of this in a first floor bathroom.

How many floors up is the flat?

UK mains pressure gets water up to about 4 stories without the need for a pump. There was an outcry a while back when Thames proposed to lower the mains pressure to reduce leaks. It would have meant anyone in a property higher than 3 stories, which is a lot of London townhouses would have needed to fit an expensive pump into their water system.

I agree with you though the cold water tank in this setup does seem to be a bit of a puzzle.

Originally Posted by SMHarman

UK mains pressure gets water up to about 4 stories without the need for a pump. There was an outcry a while back when Thames proposed to lower the mains pressure to reduce leaks. It would have meant anyone in a property higher than 3 stories, which is a lot of London townhouses would have needed to fit an expensive pump into their water system.

I agree with you though the cold water tank in this setup does seem to be a bit of a puzzle.

thanks for that

- this link, although maybe drifting a little from the main topic, does have some relevance in understanding the relationship between height & pressure for water - and is quite amusing, in its way ??

http://answers.yahoo.com/question/in...9131738AAK81LT