Pressurised System pressure drop 2 bathrooms

[arh]

Have just had a Vaillant 637HE system boiler installed with a Unistor 250. Pressure is excellent on 1st floor bathrrom. Problem is when I use the bathroom in the loft pressure is not so good. When both bathrooms are being used the loft bathroom looses almost all the pressure. I though these systems could cope with multiple bathrooms at the same time. Both bathrooms feed off the same 22mm hot pipe. Any ideas? Should each bathroom have its own connection to the cylinder?
Cylinder is installed on a custom built room at back of property on ground floor.

 

[Softus]

What pressure is the cylinder providing?

Who installed it, and why haven't you called them back to resolve the problem?

 

[arfurrrr]

What pressure is the cylinder providing?

Who installed it, and why haven't you called them back to resolve the problem?

ARH !

 

[simond]

Your uniSTOR is a very well made tin can with a hole at the bottom for the water from the rising main, and a hole at the top where the hot comes out.

You will never get any more out of the top than what comes in at the bottom. If you find that the cold water supply upstairs is similarly affected when downstairs taps are open then your problem is most likely to be a poor flow rate into the dwelling.

This could be down to a stopcock not fully open, but in practice it is more likely to be undersized pipework to the pavement or a poor water supply network locally.

The first thing you need to do is measure the standing pressure and the incoming maximum cold water flow rate. Solutions could include replacing the bottleneck (eg the pipe) or fitting an accumulator. We advise against the other option (break tank and pump) because it is noisy and doesn't work in a power cut. Also because the water is stagnant after long holidays etc in a domestic environment it is compromised.