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I live in a 8 yr old house with 3 bathrooms. This will sound really strange but when one of the toilets is flushed, they will all start to fill up and overflow for a few minutes.
If we run a bath, then all 3 toilets will also run and overflow. This seems to be when the cold tap is on.

What's going on... Help !

We have a boiler in the garage, hot water tank in the upstairs airing cupboard and the water tank in the loft. I would say that we don't have the best water pressure and the water board have been out a few times... They say it's within tolerance though. I think it's low because it really drops when two taps are on at the same time, or a tap is on and someone flushes a toilet.
I've spoken to a few plumbers and this has baffled them all, any I live in a 8 yr old house with 3 bathrooms. This will sound really strange but when one of the toilets is flushed, they will start to fill up and overflow for a few minutes.
If we run a bath, then all 3 toilets will also run and overflow. What's going on... Help !
We have a boiler I the garage, hot water tank in the upstairs airing cupboard and the water tank in the loft. I would say that we don't have the best water pressure and the water board have been out a few times... They say it's within tolerance though. I think it's low because it really drops when two taps are on at the same time, or a tap is on and someone flushes a toilet.

I've spoken to a few plumbers and this has baffled them all, any ideas ?

Hi
Can you be a bit more specific. What exactly is overflowing, the toilet bowl, or the cistern ? As much info as possible please as to what is happening, and is there any history, when did this start ?

Hi.
When one of the toilets is flushed water will pour through the overflow of the other two toilets. It's been doing it for about 6 months now, at first I just thought I needed to take the top off of the cistern and adjust the float. I had a play with the water level in the cistern and it didn't make any difference, flush one of the toilets and they all start to fill up and overflow in to the pan again. This normally lasts a few minutes except when we run a bath, then it will flow in to the cistern and through overflow for ages which is why we turn the water off to the toilets.
Hope this helps, I'll try and give as much info as I can.
Many thanks.

A bit of an update....... Turned the water off to the toilet in the main family bathroom and we've had no overflowing issues today. Wife just had a bath and the other two toilets are fine, does this explain anything ?

Ignore last comment, the main bathroom toilet is still isolated but other toilets overflow if one is flushed.