How to prove that a borehole water supply is potable and uninterrupted for mortgage valuation?

WIAWSNB

Does the property you are looking at have a filtration system? If yes, is it serviced regularly? When was this last done, and what was the test result? 
This seems a bit like insisting a vendor has their boiler serviced before sale - it's pretty much an expectation now.
If there isn't a filtration system, well, there's your answer - no supply will be potable.
As to whether the supply is reliable, I doubt there will be records kept (tho' possible, if it meant the pump shut down), so a 'statement of truth' will likely be the only way forward on this. Of course, it cannot read the future.

Penri1980

deepdown said:

@Penri1980 how did you get on with this? I'm in the same position so curious to know what you had to provide in the end. Thank you.

@deepdown I completely missed this when you asked sorry. I appreciate that it's likely too late for you but for the benefit of others, the vendor contacted the council and they sent someone out to test the water and provide the confirmation that the water was potable. They kindly paid for this and also replaced the UV filter in the kitchen sink.

As for the 'uniterrupted' question, Nationwide were happy to accept the vendor's confirmation that neither the well nor the borehole had run dry in the 25 years that they'd lived there.

This was one of many issues we had to overcome in buying an old rural property, but we got there in the end in no small part due to the support of generous and knowledgeable people on here (thanks!), so to anyone reading who is currently going through the stress, just keep going!