DIY Doctor

Shower pipes

Postby duffsparky » Fri May 20, 2011 10:34 am

Hi All,

I'm re-modelling our bathroom, en suite and installing a shower in our ground floor toilet/cloakroom. I've run low on money so I'm just concentrating on getting the shower into the ground floor toilet/cloakroom but eventually I'd like to have a shower in the en-suite and bathroom, both on the first floor, as well.

Ideally all the showers will be gravity fed and I'd like some advise on pipe sizes for the showers. The cold water storage tank was raised several years ago which gave a reasonable shower in the now removed en-suite.

Attached are 2 drawings showing my proposal, they show all shower pipework to be 22mm taking the feeds from the existing 22mm pipes beneath the bathroom floor. I'm wondering if my design using 22mm pipe throughout for the showers will give that much of a better performance over 15mm pipe, especially pipe drop D for the ground floor toilet/cloakroom shower. Is my design a bit overkill?

Also would it be better to take the shower feed(s) from as close to the water storage tanks as possible, maybe even changing the hot water tank draw-off outlet from 22mm to 28mm (if possible) and modifying the first section of pipework to suit, perhaps it would be better still to add an additional 22mm draw-off outlet point to both tanks tanks.

The cold old water storage tank is not directly above the hot water tank, it is about 7 metres horizontal distance away and raised up to give a water head height of about 2.4 metres to the first floor shower mixer valve positions and about 5 metres to the ground floor toilet/cloakroom shower mixer valve.

The 2 drawings are essentially the same except the second one has less written detail to make it clearer(?).

Thanks in advance.
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Simply Build It

Postby stoneyboy » Fri May 27, 2011 5:20 pm

You are trying to supply too many outlets from your system. As soon as the bath tap is run the first floor shower will dry up.
You probably need to consider replacing the hot water cylinder with one with dual outlets and changing the cold supply to this to 28mm. Then have two separate 22mm feeds split depending on the size of the shower heads, bath linked to smallest shower head.
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