Tip on pH testing

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JackLantern

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Dec 16, 2012
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i'm sure you already know this, but on the off chance you don't.

do NOT trust your tap water will be constant.
you may test it a couple times and it is the same, so you assume it will but that isn't the case.

e.g. i'm on city water, they use multiple wells, the yearly report shows a "average" number, and then a range.

recently when trying to figure out if some sand i used was changing my pH, i noticed the tap pH changed from 8.4 to 7.4 over a couple days.
 

ffmurray

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Oct 6, 2014
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the ph of your tap water will also change as it aerates, so even a sample from a single period will change as it sits.
 

FreshyFresh

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I would think it's more of an issue if your municipal water supply is from multiple wells. I've never seen anything other than a pH of 7.6 from My (lake Erie) municipal water supply, but I rarely measure it.
 

Rbishop

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always let that sample sit out overnight and gas off also....
 

fishorama

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We had seasonal changes in our water supply from wells, reservoirs & snow melt. The city would temporarily adjust the pH to keep pipes from corrosion but like Bob said, you need to let it sit &/or aerate it to get an accurate test.
 

JackLantern

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the water report shows an average range of over a full unit

when they recently changed wells, my GH went from 12 to 17
 

JackLantern

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i noticed that too

it goes from 7.4 to 8.2, then sometimes up to 8.4

i wasn't expecting that, don't totally understand it either to be honest. read that C02 is leaving, the water, but not sure why it would have CO2 in it.
 

dougall

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Mar 29, 2005
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oh, even my RO water climbs when it sits, from 6.4 or lower up to about 7 overnight
That would seem to indicate a problem with your RO water, it should have nothing dissolved in it, and should be pH neutral.
 

wesleydnunder

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Dec 11, 2005
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That would seem to indicate a problem with your RO water, it should have nothing dissolved in it, and should be pH neutral.
CO2 in the source water shouldn't be removed by the RO membrane like dissolved solids. Allowing the RO water to sit out overnight will allow CO2 to off-gas as it would in tap water.

In his post he notes that the ph of the RO raises to 7, ph neutral, after off-gassing CO2.

Mark
 
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