What's more powerful - electric shower or mixer combi shower?

robv_3

Assuming the mains supply has enough pressure and flow these are rough guidelines

Thermal Store / Heat Bank (30 l/m+, full mains pressure eg 8 bar)
Pressurised Hot Water Cylinder (30 l/m 2-3 bar)
Conventional System with good pump (20 l/m 3bar)
Combi (8 l/m, 2-3 bar ***)
Cheap pump (8 l/m, 1 bar)
Electric Shower (????)
Gravity Hot water system. (0.1 bar / 30 l/m

A lot of people forget the show head/rose is extremely important.

*** Combi manufactures use a temperture rise of 35 degrees when quoting l/m. Everyone else quotes 45 degree rise as hot water is normally delivered at 55 degrees. Check your combi manual for its real rating at 45 degree rise.

another point is it is unlikely you will have a shows requiring more than 10 l/m of hot water.

ahfh1

House_Hunter wrote: »

My firsts thoughts would be - whats your connection to the mains like? Old lead pipes of nice new low friction blue plastic?

You can buy/hire a flow meter and pressure gauge set - tip if you've got an outside tap test it on that one , saves spraying water all over the house!

Tip 2: most utility companies will measure the flowrate/pressure of your supply if you get them round for a quote Npower/BG etc etc...obviously you wouldn't pick them unless you have more money than sense, but saves you a few quid having to hire a meter...

I will check the pipes. Which is better - old lead pipes or low friction blue plastic?

Seeing as a plumber will be coming round to install the boiler and shower, would it be safe to assume he will have a flow meter and pressure gauge set? Saves me from buying a set or calling NPower/BG etc.

House_Hunter wrote: »

Then I would ask what your piping to the bathroom is like 18mm or 15mm pipes?

As obviously pressure and flowrate vary with them both - 15mm will give a lower flowrate but better pressure maintance, where as 18mm will give you a drop in pressure but higher flow rate....

So there is a trade off in terms of pipe width vs flow rate vs pressure, and there is no ideal pipe size?

Cheers

House_Hunter

Nice new blue plastic is much better....lower friction, less pressure drop..

The old lead one's are oftern large diameter as well...which although giving you a good flowrate, results in a lower inlet pressure to your property. Once this pressure has been lost, a traditional combi can't really get it back again..

Re bathroom pipes, my personal opinon is 15mm throughout...though I am no plumber.

Most plumbers/boiler installers will have a pressure/flowrate testor with them, they aren't very complicated.

Do you have a combi at the moment? If so you can measure the flowrate simply yourself - I used an old 4pint milk bottle (2.27 litres). Time how long it takes to fill with the tap fully open...and heyho...you've got yourself the flow rate.

As before, if you've got an outside tap is best to avoid spraying water everywhere..