Shower stops when loo is flushed...

[Fab41]

One week in to new house, and looks as though we have a water pressure problem. Shower was running, loo was flushed and the shower stopped until loo refilled. Pressure isn't great in kitchen where I presume mains comes in (water meter is under sink).
I will call Southern Water today but any ideas or suggestions?

Upstairs radiators don't warm up beyond tepid either, although I guess this is a separate issue.

have you got a combi boiler, and a shower mixer with thermostatic control?

We have a gas Rayburn nouvelle which is a gravity fed system, hot water fills up two tanks, as I understand it. Shower is thermostatic, it has three settings of high, medium and low, and a temperature dial. Also has a low flow warning light.

That is about the extent of my knowledge...

I think you mean you have a hot water cylinder. What colour is it?

You say that the shower "has three settings of high, medium and low, and a temperature dial. Also has a low flow warning light""

This is almost certainly an electric shower, and is not fed from the cold tank or the hot water cylinder, which are not relevant to the problem. Electric showers are fed with cold water from the main.

You say it happens when the WC cistern is refilling. This means that cold water is being drawn from the pipes, which is a cause of a drop in cold water pressure. This will cause an electric shower to cut out to prevent the danger of scalding.

It is possible that the pipe layout is bad, allowing the WC to take too much water so that there is insufficient for the shower.

You could probably make a bodgy fix by reducing the water flow to the WC cistern, for example by fitting a stopcock and turning it so it is nearly shut. A better fix would be to examine the pipe layout, which is probably badly designed or installed, and to correct it.

Is this a new house, or an old one that has been inexpertly worked on?

We have an electric shower in our en suite. We don't lose the water when the loo is flushed but we lose the heat, so if you're in the shower and someone flushes the loo elsewhere in the house the shower suddenly becomes freezing cold - horrible.

The main bathroom has a power shower and that doesn't seem to be affected by the loo being flushed.

I have no idea why this is the case....

" so if you're in the shower and someone flushes the loo elsewhere in the house the shower suddenly becomes freezing cold "

I think it will be detecting that there is insufficient flow, and turning off the elements to prevent scalding.

House is old, we have just moved in.
I have got a plumber coming over some time next week, as there was another shower in the ensuite which has been removed.
I will get him to have a look at the pipe layout.
It seems madness to not use the hot water from the boiler as it runs constantly on tick over (gas) and we have loads of almost scalding hot water.

Thanks for advice so far.