Boiler/Combi Question

danielfulshaw

Hi guys

Quick question. We have a 4 bed detached house with (currently) 1 bathroom and a Combi. When we run the taps in the bathroom and flush a toilet the usual combi thing happens which is the flow is temporaily reduced. So far , so normal.

But - we want to install a shower/wetroom downstairs. The installer has advised going for an electric shower (great as gas prices are shooting up) but he has said that it will draw water off the mains so won't interfere with the operation of the combi. Is this correct? Say we have the bath running and the shwower on? Will this not affect the flow in both? If we have the washing machine on, which I also think draws water directly from the mains inlet pipe, will this reduce the shower pressure?

If I'm right and it does, what is the best solution to all this? Will a pump help, hinder or make no difference? I'm concious that we can get a bigger combi but that is expensive and the other one is just 3 years old. I am so annoyed about this because I was assured by a rogue plumber that the combi would be good to do both..when clearly that's rubbish! Please advise as don't want to rely on bad advice.

evilgoose

I must admit I'm not entirely please with combi boilers after having been forced to swap from the old system (hot tank and cold tank) when my solid fuel boiler burst.
The advantage was that with a cold water tank in the attic it helped maintain pressure when a few taps/the shower in use.
I'm not a plumber, but from what I've read I dont believe that a pump will help you as its still drawing its 'in flow' from the mains so will be starved by several devices in use simultaneously.

danielfulshaw

Thanks - anyone else have any ideas?

Snow_Dog

You will find that with an electric shower, when it is running you will get a slightly reduced flow on all hot and cold taps in the house than when its not running. This is because you only have a finite amount of water that you can get out of your cold main at any one time.

This amount is determined by pressure and the bore of the main pipe. By turning on one tap/shower you are reducing the amount you can pull off from other taps.

The advice for using an electric shower is sound as the main concern is the amount of hot water the boiler can produce, this is usually listed as litres/min for a given temperature rise.

danielfulshaw

Thanks - yes that makes logical sense and is what I suspected. So the only alternative would be to store the water and basically fit a tank - doable but expensive for one shower.

Snow_Dog

You may have high mains pressure and a good diameter main in which case the diference in flow when the electric shower is running will not be very noticable.

I suppose one way of checking would be to experiment, if you are running the sink in the bathroom with the cold tap, how much difference does turning the kitchen tap on and off make?

500 posts! Its only taken 2 years

spakkker

Since no one is getting thanked I will throw my 2p worth in; What are you worried about? Can you not put up with minor temp. changes?
What about a thermostatic mixer?

amcluesent

>great as gas prices are shooting up<

On a like-for-like, the kwhs price of gas is still a lot less than leccy.

Snow_Dog

amcluesent wrote: »

>great as gas prices are shooting up<

On a like-for-like, the kwhs price of gas is still a lot less than leccy.

Nice to have a back up for when the boiler goes bang.

danielfulshaw

I'm 'worried' about getting hood winked a second time by a plumber that couldn't give a damn once the thing has been fitted and we can't run a shower and have a bath at the same time or put the washing machine on. Not much use having a second bathroom really if that happens is it and you both have to leave the house for work at 6 in the morning??