Water social tariff and PIP/NS ESA

Hi, I receive new style ESA and PIP. We have revived our water bill which is unmetered at £1300 a year.. a massive increase. We've been told we can't have a meter yet due to some complications with the property location. I'm thinking I'd apply for a water bill social tariff but I'm not sure if PIP is included as income? My wife's salary is only £9k a year but if we add both ESA and PIP we will exceed the cut off for a social tariff (I think it's £16k).

Has anyone any experience of this?