Tap Water Stats Again.

[hamfist]

In a follow up thread to my other tap water stats thread. I have just realised that even though my water comes out of the tap at pH7.4, after 2 days standing in a bucket, letting the chlorine diffuse off, the pH is up to 8 ! Not an earth shattering surprise as dissolved chlorine is quite acidic, but I am surprised how much it changes.

Bought my test kit only a few days ago and have been playing around with it. I had been a bit puzzled as to why my tap water was 7.4 out of the tap, yet all my tanks are at 7.8-8.0. All seems clear now !

 

[N0body Of The Goat]

Like I posted in your other thread, my tap water's pH in Bitterne is 8.2 after adding Aquaplus (de-chlorinator). You should find kH and gH to be in the ballpark of 200/260mg respectively per litre.

Nitrate in our area can vary in the 20-50ppm ballpark, which makes it very handy to have a "high-tech" planted setup. The plants will typically use ~5ppm per day, while the setup ideally needs a carbon dioxide system, which will lower the pH back down to ~7.5 at 30 bubbles per minute

 

[PDSimon]

there is more c02 when it comes just out of the tap...

thats what all those bubbles are when you do big water changes I think.

c02 brings down the pH so... that may be the main contributor

 

[Bignose]

PDSimon has it right. Water companies will often dissolve CO2 into the water to make it more acidic -- less mineral build up in pipes and the like. The CO2 forms carbonic acid with water CO2 + H2O <--> H2CO3, and this is what makes the water acidic. So, when the carbon dioxide in the water equilibrates with the atmosphere, the water is left with a higher pH.

The amount of chlorine in the water is actually quite small, and has a minimal effect on the pH, especially compared to the effects of the CO2. Also, are you sure that your water supplier used chlorine? It is far more common for water companies to use chloramine these days, simply because chorlamine is far more stable in the water, and more deadly to microbes so less of it is needed that straight chlorine gas.

My tap water comes out 7.2-7.4, but always settles around 8.2-8.4 in the tank.

 

[SlyPolak]

So if water companies dose with C02 for that reason, wouldnt it be just cheaper and easier to do water changes than do the whole C02 injection thing for your aquarium plants

 

[Bignose]

So if water companies dose with C02 for that reason, wouldnt it be just cheaper and easier to do water changes than do the whole C02 injection thing for your aquarium plants

CO2 dosing injects CO2 continuously. Water changes would temporarily bump up CO2, but it will gas off quickly. It will gas off in less than 24 hours in still water, I suspect it is all gone within 2 hours in a tank with water moving.

 

[ian]

thats the way forward for planted tanks then...2 hourly water changes!