High Ph Reading

flippajh · Mar 29, 2009

Hi, wonder if you can help, the pH from my tap reads about 7.2, but the pH in the tanks reads about 8, is it natural for the pH to rise like that or is something going wrong, I've read about pH dropping but can't find anything about it rising in the tanks.

Thanks

lyotim88 · Mar 29, 2009

what do you have in the tank? what kind of rocks, etc?

Bignose · Mar 29, 2009

Probably carbon dioxide dissolved in the water that is gassing out. Carbon dioxide dissolved in the water makes an acid, water companies add CO2 to the water to keep some of the basic dissolved minerals from coming out of solution and caking up your pipes. When the water sits, this CO2 will leave, and you end up with a higher pH because there is less acid in the water.

flippajh · Mar 30, 2009

Its 180 ltr, with a very large piece of bogwood, but this has been in about a year now, and at Christmas (Presents!) I added a terracotta plant pot and also two stones which are an orange colour with kind of quartz running through them.

The only thing i've done slightly different over the last 3-4 water changes, is we had a water softener added and I've been doing the water changes from the tap in the kitchen which is still hard water, but recently for ease of getting to a tap I've been using the water from the tap in the bathroom which is softened water. Readings from both taps were the same, around 7.2/7.4. Could the pH be affected by the water hardness? I suppose I ought to get a GH or KH test kit, my API test kit didn't include these.

Bignose · Mar 30, 2009

Take a clean glass of water. Measure the pH of that water. Let the glass sit out overnight to 24 hours, and then measure that pH. If the pH of the sat-out glass has increased, it is the dissolved carbon dioxide in the water that gassed out. This is the very first thing to suspect when the pH rises like this. Do this test, and if you don't get the pH rise as expected, post back and we'll ask some more questions to get to the bottom of it.

BenPursglove · Mar 30, 2009

Bignose said:
water companies add CO2 to the water to keep some of the basic dissolved minerals from coming out of solution

Never heard of this, you live and learn.

I think the water softener you mention has a part to play in this or something in the tank pushing the Ph up. Try what Dr. Honkerface has suggested with leaving some water standing and testing after different periods of time and post back. I wouldn't fork out for CH or GH tests as they will not be of much use at the moment...

Bignose · Mar 30, 2009

BenPursglove said:
I think the water softener you mention has a part to play in this

It is very unlikely that a typical water softener would affect the pH. Water softening simply takes the Calcium and Magnesium ions out of the water and replace them with Sodium ions. This has virtually nothing to do with pH, because pH is a measure of the concentration of H+ ions. I cannot say zero effect on the pH, because the change of the ions in the water does change some of the complex reactions that go into the buffering of the water. The molality of the water will change a tiny bit, which will change the ionic strength a little. But, the effect isn't going to be large -- a few thousandths to maybe a few hundredths of a pH unit at the most.

flippajh · Mar 31, 2009

Bignose said:
Take a clean glass of water. Measure the pH of that water. Let the glass sit out overnight to 24 hours, and then measure that pH. If the pH of the sat-out glass has increased, it is the dissolved carbon dioxide in the water that gassed out. This is the very first thing to suspect when the pH rises like this. Do this test, and if you don't get the pH rise as expected, post back and we'll ask some more questions to get to the bottom of it.

Thanks for this will do experiment this evening and post results.

flippajh · Apr 1, 2009

Bignose said:
Take a clean glass of water. Measure the pH of that water. Let the glass sit out overnight to 24 hours, and then measure that pH. If the pH of the sat-out glass has increased, it is the dissolved carbon dioxide in the water that gassed out. This is the very first thing to suspect when the pH rises like this. Do this test, and if you don't get the pH rise as expected, post back and we'll ask some more questions to get to the bottom of it.

Ok, answers to the experiment.

pH level taken direct from tap reading
Kitchen Non Softened Bathroom Softened
7.2 7.2

pH taken from water left 24 hours
Kitchen Bathroom
8.4 8.4

So absolutely no difference between softened and non-softened water, it has risen quite substantially over 24 hours, but obviously dropped slightly in the fish tanks, as the readings I'm getting from the tanks are around 8. How interesting, but it sounds like this is what is supposed to happen, so all good then?

Thanks

Philippa

Bignose · Apr 1, 2009

The overnight pH increase is as I posted above in all likelihood the carbon dioxide gassing out. The pH rise in this case is normal, and 1.2 pH units is pretty typical.