Water in bore pH dropped

[nickcar]

 I wonder if there are lots of knowledgeable people on this forum who know about water from bores.  I drilled my bore about 10 years ago and it has supplied me with water satisfactorily since then.  To begin with, the bore is about 25 m deep and came up with black stuff in it. In the last few years it has seemed as though it is rusty. None of this is a problem as I have a big meter and a half high filter to clean it before using in the house and further proper drinking water filter for drinking .

 

About one year ago I suddenly realised the pH of the water had dropped from about 7.1 to 5.5  I only realised this because I have a swimming pool and use the water to top it up occasionally.

 

I believe I can buy an in-line filter to increase the pH but I am most curious to know why it would change like this. The reading tells me it can be caused bye Excreta  but I would find this very surprising as there are no houses close by, two houses within a kilometre. There is a pig farm about 1 1/2 km away but surely that would be too far to cause it 

 

Thanks for anybody can you who can share a clue on this.

 

Nick

[bankruatsteve]

It could be temporary - like from an infusion of rain water which is usually somewhat acidic.  You say this has been going on for one year?  Increasing the bore depth should help but determining the cause would be good in any case.  Any big changes in the vegitation or topography?

[nickcar]

 Yes one year, so it is unlikely to be temporary. No changes of any significance at all close to the bore. I was just remembering last night that my local klong  which is about 200 meters from the bor  is seriously polluted by pig excretion.  To the extent that the local farmers cannot grow Hom Mali rice  any more because it just dies. They have to grow the hard rice types.  This has been served for three or four years so it might have spread into the ground water, what do you think? 

[bankruatsteve]

Sounds like high octane pig scat!  Its decomposition might explain the acidity from higher CO2 levels in the ground water. (?)  That's where a deeper bore should help.

[nickcar]

 May I ask  if you are expert on the subject?  Forgive me for asking and I appreciate your opinion one way or the other.  I am kind of surprised and disappointed that we haven’t got lots of experts commenting.   How deep do you think the bore should have to be to improve the water? Is it possible there are dangerous poisons in the water (fecal coliform) ? The drinking water is passed thru another filter that has 3 stages plus reverse osmosis. 

Thanks

 

nick

[bankruatsteve]

I am not a geologist.  Your situation is similar to a relative's farm years ago.  He needed to go deeper with his bore due to ground water contamination.  The deeper the bore, the more "filter" is provided by the earth.  You only mention a slight decrease in pH which can be the result of organic decomposition.  Suggest you get a sample tested and decide from that.  The depth of the bore would depend on a test that yields the result you need.

[tjo o tjim]

Instinctively I agree with @bankruatsteve is saying, but no expert either hence not posting earlier. 
 

It might make sense to have the water tested.  Treating it properly (holding tank and all) might be needed beyond just filtering and neutralizing it, so you are best knowing what you are up against.