Tee connections for bath and shower.

[mark.hannah]

I am about to connect the plumbing for the bath with an electric shower over it. Currently, the cold water pipe runs past the bath, with a tee off for the cold tap, like so

==========++=========== cold supply pipe | | | | | | feed to bath tap

To supply the shower, should I take another tee from the cold supply pipe, or from the feed to the bath tap?

i.e., should it be like :-

==========++=========== cold supply pipe | | | | | | bath ===++=== shower

or

======++ ======++======= cold supply pipe | | | | | | | | | | | | bath shower

[Andrew May]

You don't say what size the pipes are. If the supply pipe is 22mm and the feed is 15mm then you could make an argument for taking the feed to the shower from the supply. However since you are unlikely to be running the shower and the bath at the same time I would probably choose whichever is the easiest and neatest to plumb.

I am sure others will have other ideas.

Andrew

[mark.hannah]

The supply pipe is 15mm - and the feed to the bath is 22mm - which does seem strange to me. The rising main comes into the bathroom, and is connected to a 15mm pipe, which passes by the the basin, then the bath and then off into the kitchen.

The direction of flow in the diagrams is right to left.

Mark.

[David Hansen]

On Fri, 22 Jun 2007 02:17:16 -0700 someone who may be [e-mail] wrote this:-

It was probably convenient to make the change from 15 to 22mm at that point. Often this is done at the bath tap, where it is more fiddly.

Personally I would remove as many things as possible from a rising main that diameter and feed them from a cold water storage tank instead.

In a situation of mains pressure cold and gravity hot water, which is what I assume you have, a venturi shower is often a better thing to go for. No electricity to bother with.

[Roger Mills]

Assuming that you won't be running the bath's cold tap at the same time as the shower, it doesn't matter a damn - do whatever's easiest.

Are you sure you really want an electric shower? If you have a hot water storage tank, you will get a much better shower by using a shower pump from that rather than trying to heat it with electricity in real time. It will also be cheaper to run if you use gas to heat your water.

[mark.hannah]

Well - good question on the electric shower - the main benefit of it to me would be instantaneius hot water. All my previous homes have had combi boilers - so I'm not sure how long it takes to heat a water tank?

Mark.

[David Hansen]

On Fri, 22 Jun 2007 06:21:46 -0700 someone who may be [e-mail] wrote this:-

Getting hot water instantly is overated by many. It is often far better to heat the water relatively slowly and then release this rapidly.

If you have not used an electric shower before you may be surprised by its lack of performance.

I doubt if you have a hot water tank, you almost certainly have a hot water cylinder. How long this takes to heat depends on several factors:

1) the power of the boiler

2) whether the boiler is just heating the cylinder

3) the form of primary circulation, pumped or gravity

4) the efficiency of the heat exchanger within the cylinder

5) the effectiveness of the insulation on the cylinder

6) the temperature of the cylinder contents when the heating starts

7) the volume of the cylinder

[mark.hannah]

One question - does the cylinder have to empty completley before new water is added and heated?

And I don't think instantaneous hot water is overrated when you're late for work in the morning, and 2 people have already had a bath before you!

[David Hansen]

On Fri, 22 Jun 2007 07:23:03 -0700 someone who may be [e-mail] wrote this:-

The cylinder is never emptied, other than for maintenance. As hot water is taken off at the top so cold water replaces it at the bottom. It is actually the pressure of the cold water that pushes the hot out of the cylinder. Provided the thermostat is in the right place this will start the boiler firing if the draw off is significant, or the cylinder is cooling.

If the system is properly designed and sized three people having baths one after the other is no problem at all, assuming that they spend enough time in the bath to wash themselves properly. With a typical combination boiler this operation would have taken longer anyway, as people would have waited for many minutes while water trickled into the bath.

There are a few forms of instant hot water heating that can produce a lot of hot water rapidly. The only one people are likely to see in domestic buildings is a thermal store/heat bank.

[Roger Mills]

With a decent boiler and a fast recovery cylinder, you should have lashings of hot water in less than 20 minutes.

Your combi boilers may well have been about 30kW - whereas the most powerful electric shower is no more than 10kW - thus severly limiting the throughput of hot water which it can produce.