Combination boiler in a four bedroom busy house.

10 Nov 2008
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United Kingdom
Hi, this is my first time in here so please forgive any bad protocol. :eek:
We have a large four bedroom Semi with four occupants.
We had the boiler replaced several years ago by a family friend plumber who said they knew what they were doing.
We had a standard boiler with cold and hot water tanks, one bathroom with a bath and shower, twelve radiators, a kitchen and downstairs loo/basin.
Unusually the hot tank was in the loft.
He disabled the hot tank and fitted the combi boiler, leaving the cold tank in the loft to feed the upstairs taps.
He told us we may need to replace the shower as the new system may not be compatible.
The shower seemed ok but was unpredictable.
A couple of years later we replaced the shower but it is still very unpredictable, that plumber disabled the cold tank and told us it should not have been left up there.
Testing the system and reading about combi boilers I am wondering if it is possible to have a shower without the pressure dropping and heat stopping altogether whenever any other tap in the house is used.
At present you have to get everyone to promise not to turn anything on if you want a shower.
I am wondering if a combi boiler is simply not appropriate for our house.
I asked someone from British Gas who said you can fit a hot tank to a combi boiler to hold hot water for showers but can't find anything online.
Does anyone have any useful thoughts to offer?
Is the only way to get a shower which stays hot while other people use taps to go back to having a standard boiler with hot tank?
How do people with en suite bathrooms cope?
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Firstly, most combi's will only cope with a single point draw off of hot water. That won't change without some serious cash/reworking of your system. Here are some suggestions

Fit an electric shower

Rework piping to use combi to heat up a cylinder and fit a balanced cold/hot water flow to existing shower (this is fairly major and may not be possible with your make/model of combi.

Rip out and start again with an unvented cylinder to provide high flow rates for multiple hot water draw off points

Others on here may have good suggestions too
Although an unvented cylinder sized to suit your propery and needs will always be the best option, you could look at the Vaillant Ecotec Plus 937.

You may find that this will just about deliver 2 9 l/min showers similtaneously.

Wheter you go for this or the unvented you need your mains pressure and flow rate tested.

You will need at least 20/25 l/min and around 2 Bar to get your monies worth out of either of these systems and to get them to work properly.
Thanks for the advice, I have asked about electric showers but people say they are low pressure and only last two or three years.
This may be the only economic answer though.
When you say rip it out, do you mean the boiler as well?
Maybe we should have left the cold tank in place and added an electric shower to prevent the pressure dropping.
Has anyone heard of an electric shower with it's own hot tank as this would get around the pressure problem.
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it sounds like your water pressure/flow is poor if you cannot use more than one tap at a time, an unvented cylinder is the best way to go but you will have to either upgrade your incoming supply or have a break tank and pump , with this setup you can keep your combi to heat the unvented on an s plan and have the hot water side just for the kitchen sink.
Thanks for that, if I turn on a hot tap and then cold tap on the same basin, the hot tap slows down and goes cold. How do I test the water pressure?

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