Simon ness

I am in Wales and am deciding whether to get mains water or not. I have a constant supply of spring water piped through my property ( 1 gallon a minute minimum . It goes into an inspection chamber then piped further down the hill. It looks to be very clean but not tested yet. It will cost me £4K to get mains water so wondering if it makes sense to simply use the spring water instead - cost being the main factor. The spring is below the property so a pump would be needed. I don’t think a large storage tank is needed however as the spring water is constant irrespective of rainfall and would be replenished every day. The tank would need to overflow back into the piping. I assume I need water authority approval I guess as they have piped the water through my property and built the inspection chamber. I think the piping enters a canal about 100 metres further down the hill. Any advices appreciated.