DIY Doctor

Installing seperate Shower unit

Postby Markyb2511 » Mon Mar 28, 2011 3:18 pm


I am thinking about installing a shower unit into my downstairs WC. as I am just at the thought stage at the minute I just want to know the basics involved regarding the pipework.

Do I simply connect the shower waste pipe to the existing pipe in place for the tiolet and as I am going to be using a mains mixer shower head instead of an electric unit do I just tap into the hot and cold water at the taps?

Please excuse my ignorance on the subject.


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Simply Build It

Postby Kenj » Tue Mar 29, 2011 10:20 pm

Yes you are correct about the waste.

However, it may be neater if you can tee into the soil stack on the outside wall of the toilet (assuming it's on an outside wall), rather than in the toilet itself.

The water pipework is a little more complicated.

If you have high mains pressure cold water and gravity fed hot water, you may need to fit a pressure reducing valve in the cold flow, to prevent a pressure imbalance resulting in a cold shower.

If your hot water comes from a Combi boiler then the pressure will be equal, but you may not get a very powerful or hot shower.

The following excerpts are from Triton and Aqualisa shower installation manuals, available online.
1. The pipework should be installed such that the flow is not significantly affected by other taps and appliances being operated elsewhere on the premises.
(This is to prevent you being scalded if someone runs a cold tap while you are showering, or freezing when someone runs a hot tap.)

2. Gravity fed hot and cold supplies. To minimise pressure loss we recommend that the hot and cold supplies are run in 22mm as close as reasonably possible to the mixing valve before reducing to 15mm.
(You are unlikely to have 22mm pipework in a toilet.)

Also check that the mixer shower that you buy is suitable for high (mains) pressure, or low (tank fed) pressure. Many are suitable for both, but not all.

I have fitted a shower into a downstairs toilet, and because of these issues decided to fit an electric shower, fed from the cold mains pipe. To fit a mixer shower may be possible, but will need some careful thought and planning.
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