I had a negative test on my Borehole water test - but close, in that the pass was zero and I had a 2 on the 37 deg incubation test. I have had this borehole for a couple of years. It is 65+m deep and sealed well at the top with neat OPC 2m deep or so. There are in all over 100m of 40mm pipe to the house/irrigation tank. (currently just being used to refill irrigation tank (20m3) and refill swimming pool.

I tried to sanitize the pipes last time but I imagine I failed and that is what I want some help with - though it may have been my solution for sterilising the bottles/mishandling at the time of sample (this time I have sterilised bottles from the pharmacy). Actually my Geologist, who was responsible for all the planning formalities and the design etc, said it was so problematic to pass this test that I shouldn't bother and everywhere locally (boreholes) uses the 'same' water and it is safe to drink! But since there is the outflow from my modern sewage treatment plant nearby and I have have elderly relatives in the house I thought I should have the test. From what I have read I shouldn't be concerned about the sewage given the situation here and this post is about sanitising the pipes.

So I did the sums for how much water is in the borehole/pipes and it is very little indeed, needing very little chlorine, I thought. I ended up putting loads down but didn't seem to be able to taste it at the house. Firstly, I guess there is no issue with putting a massive dose of chlorine down the borehole so long as it tests as having no chlorine (using a swimming pool dip stick) before I take the sample - am I right about this? Secondly just getting the chlorine down there is a bit problematic, in the end I just poured chlorine granules in the pipe and washed it down with several bucket loads of water - I can't see any benefit to trying the dissolve the granules as they really don't dissolve easily.

So how long should I leave it after dosing before trying to flush the system through - perhaps start immediately? Should I stop pumping as soon as I taste/test chlorine and leave it for an hour - then flush then test? Is it right to think of it as a stable volume of water where more just percolates through when water is taken rather than a river? The test isn't cheap so perhaps I shouldn't attempt it unless I can actually taste/measure chlorine at the house.

Any advice welcome

Bore hole tests - bin there dun that and got the tee shirt.
There should be a take off point AT THE BOREHOLE HEAD that is just used for taking the test sample. You are testing the bore hole water not the water delivered somewhere else on the system. The sample take off point should be galv. iron and should be capped unless in use. There should be a tap some 30cm before the end of the sample pipe. The method of sampling is to run the pump for 5 mins through the sample pipe, turn off the sample pipe tap and empty the water in the sample pipe. Then with a gas torch sterilise the end of the sample pipe and then fill the sample bottles from the sample pipe.

Things that can help produce a good result.
1. run the bore hole pump through the sample point for 12 hours before sampling
or
2. dump a couple of lts of hypoclorite bleach (without fancy names or perfumes, about 40p / ltr here) into the borehole, leave over night then run the bore hole long enough to flush the borehole and sterilise and sample as above.

Also make sure that the well head is properly sealed so that nothing can get in past the output pipe.

A good test not withstanding I have been told that people will become accustomed to (immune) to a couple of strains of bacteria that are constantly present whilst a visitor will spend 3 days on the loo. The holiday tummy syndrome. So your Geologist probably has a good point.

I have also been told by a water inspector that a borehole in constant use very rarely gets bacterial contamination.

Posted By: GotanewlifeSo, I shall dump a couple of litres of bleach into the well and leave overnight, then I will run the water out of the local tap for 2 hours and take the sample mid-stream. Then hot foot it off to the lab before it closes at lunchtime (only open 3 mornings a week!).

Go for it ! but if you can immerse the tap in bleach as well, because taps are v.good at collecting stuff that crawls up inside and deposits all sorts of sh1t
If sampling has to be done on a regular basis it would be worth putting in a sampling point at the borehole head. Both my boreholes are in plastic pipe but have a galv. pipe about 50cm long teed off at the borehole head (with the tap at the tee) for the purpose of sampling