Just noticed on my Thames Water bill & associated bumph:
Water Pressure
We aim to provide water at a reasonable pressure at all times. If your pressure falls below 7 mteres head for an hour or more on two occasions in any 28 day period you can claim £25.00. The payment will only be made once in any year.
7 metres head is approx 0.7 bar I think.I guess they're fairly safe, knowing that probably none of their domestic customers has the apparatus to measure & record pressure satisfactorily to make such a claim :-)