Reduced shower pressure, any ideas?

[boxster9]

Does anyone know what the problem may be here. Whenever we use the shower and another tap is opened (could be anywhere in the house) , the pressured from the shower is reduced to a mere trickle. It seems we can't have two showers running at the same time, which defeats the object of having two bathrooms in the first place.

The mains pressure is good, so it must be something to do with our plumbing setup.

Any thoughts ?

[boxster9]

The house is approx 10 yrs old. There's no hot water tank in the attic. We have one of those 'Megaflo' type cylinders in the airing cupboard , an 'Oso indirect unvented water system'.

Previous house we lived in we could have three showers running at the same time with no loss in pressure.

[boxster9]

Thanks all. Although I mentioned Megaflow, it's actually an 'Oso' brand but the cylinder looks identical to a Megaflow.

I'll try to post a picture of the setup.