DIY Doctor

I'm having a combi boiler, do I need to change my showers?

Postby deguerre » Mon Sep 06, 2010 6:49 pm

Hi, I've had a couple of quotes a few months ago to have a combi boiler installed. I have decided to get it done but it was a while ago and my memory is hazy, I have 2 showers in the house, I know that there maybe a problem with 1 or both of them & it/they they will need replacing when the boiler is done. One is a power shower with a pump in the airing cupboard, the other is a 'gravity fed' (is that what they're called?). What is the deal with this? Why do they need replacing, what is the reason for it?

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Postby Perry525 » Tue Sep 07, 2010 12:31 pm

A combi boiler will be difficult to live with.

They only produce enough hot water for one tap at a time.

You have two showers, only one will work at a time.

If you are using a shower and someone flushes the toilet, you may be burnt by the sudden rush of hot water.

If someone turns on a tap, you will be frozen by cold water.

Your showers are low pressure as such they will work at mains pressure. The power shower will be redundant as that will be at mains pressure.

If you have a family, where perhaps two or more people want to wash/shower/bath at the same time, or even clean the car or run a washing machine, all these things will alter the water pressure without warning, avoid a combi.

If you or perhaps a future family living there, may have young children, do keep in mind that when your water supply is cut off, you will have no water!

You may find yourself driving round the country looking for a supermarket in the middle of the night, trying to buy bottles of water to flush the loo, or wash your child.
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Postby plumbbob » Tue Sep 07, 2010 11:39 pm

It is now accepted that the use of stored water in domestic situations is considered unacceptable as such water cannot be considered as "wholesome" mainly due to the possibility of contamination.

All new and nearly all upgraded installations use unvented pressurised systems that do not rely on stored water. Modern incoming mains guarantee good water pressure and the water companies strive to provide consistent supplies.

I would say pretty much 100% of new boiler installations in the average single bathroom house are combi boilers. Many larger properties successfully still choose combi boilers as their preferred method of heating, but if the house has two showers careful consideration must be given to mains supply and boiler capacity.

Existing showers may work with combi boilers. The only way to be sure is to check with the manufacturer. Some shower valves need flow reducers fitted and some will not work at mains pressure.

Integrated power showers are never suitable for mains pressure but if the pump can be removed from the circuit, the shower can be retained as it should be suitable for high pressure.
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Postby Perry525 » Wed Sep 08, 2010 10:50 am

Now you have two points of view.
I have indeed experience of cold water tanks with dead birds in them.
However, most plastic tanks have fitted lids and as overflow/vent pipes tend to be long, nothing is likely to find its way into the tank.

The, "all new" is a bit to inclusive, and is obviously not true as you can still buy traditional boilers.

In the last five years, we have had our water supply interrupted three times, on one occasion we had our garden tap running 24 hours a day for three days trying to clear the clay from the supply. These accidents are not the fault of the supplier, they are due to mains bursts and accidents on building sites.

As you write, many larger properties use combi boilers for their heating, there is no issue with this.
But, the issue is, the supply to multiple outlets and the frustration and danger this leads to with large families, mainly children who do not think, before flushing the loo or running a tap.

Existing showers may work with combi boilers, again they may not. This is an added expense.

One can easily remove a pump from a power shower and the shower will still work, after a fashion!
You will not get the same delivery of water, the same power. And of course the shower may run dry or cold, or perhaps burn you, or your family.

Why change a perfectly good working system for something that is second class?
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