Cause for decrease in water pH from well head to faucet?

[tkeoki]

*reposted from pump and well forum as I think this forum is more appropriate for question.

I just had my water tested at both the well head and at an indoor faucet.

The plumbing from the well head consists of 15' of 1 1/4" galvanized pipe to an old 120 gallon galvanized pressure tank. From the tank is 250' of 1 1/4" sch 40 pvc and 20' of 3/4 pex.

pH decreased from 7.36 to 6.42 -- any idea what could cause that?

Also, Zinc increased from undetectable to 0.10 ppm, and Manganese tripled from 0.02 to 0.06 ppm. I have manganese bacteria coating the insides of my plumbing.

I assume the old galvanized pipe and especially the old pressure tank is the reason for the zinc and manganese increase, is that correct?

Here's the complete water test:

 

[Reach4]

I presume you are implying that you took the samples within a day of each other.

You cleaned the faucet with vinegar recently? You cleaned the well with chlorine bleach or did well shocking recently?

I suggest getting your own narrow-range pH test paper. The next time I buy something like that, I intend to try the Hydrion Urine & Saliva pH Paper 5.5-8.0 I am not happy with my really cheap test strips.

I would not expect galvanized pipe to produce manganese.

 

[Sponsor]

 

[tkeoki]

Samples were taken within 15 minutes of each other. Samples were then mailed to Texas A&M testing lab.

No recent chlorine/vinegar cleaning of well or faucet.

I'm just guessing, but I'm thinking for the manganese, a lot of the manganese has oxidized and precipitated out in the 120 gallon pneumatic pressure tank, and the water then gets some of the manganese from that precipitate? Also, again, not sure of the chemistry involved, but I'm thinking the water running through 300 ft of pipe coated with manganese bacteria slime adds some manganese to the water?

Could the pH change be from the added CO2 in the pressure tank and then air contact coming out of the faucet?

Thanks for the info on the pH paper -- I've been looking for a good quality pH testing method.