Ph level of water from faucet and RO system

[David Lindquist]

From the interweb:

Reverse osmosis water purifiers will reduce the pH of drinking water. Because reverse osmosis removes the minerals in water the water will then react with carbon dioxide upon exposure to air to form carbolic acids, thus lowering the pH.

That should be carbonic acid, carbolic acid is an old name for phenol. Maybe being a little nit-picky about mis-speaking-mis-spelling but we are talking chemistry here.

David

[djdister]

That should be carbonic acid, carbolic acid is an old name for phenol. Maybe being a little nit-picky about mis-speaking-mis-spelling but are are talking chemistry here.

David

Thanks, I need to steal from a better website...

[Maris Rusis]

For the point of view of electrochemistry, an old laboratory specialisation of mine, it is theoretically impossible to measure the pH of pure water using a glass electrode. The hydrogen (and hydronium, etc) ion strength and ion mobility is just too low to arrive at a stable result. Interference from dissolved gases (CO2 mainly), temperature gradients, and assymetric flow, drift, and diffusion across the glass electrode, and contamination from the electrode itself, masks the result. That's why pure water is characterised by conductivity measurements rather than PH with 18.2 megohm water being theoretical perfection. Just dipping a PH electrode into ultrapure water destroys it in seconds.

Less pure water with plenty of mobile ions in it can be characterised by a PH value measured with a glass electrode BUT anything remotely like potable water is still a solution so dilute that it has no buffering capacity. The result of this is that it doesn't practically matter what PH water you start with. The starting water PH is totally (totally) overwhelmed by ions you dissolve in it when making up photographic processing solutions.

[Steven Ruttenberg]

I agree,but the point of measuring my water was to ensure it was not the culprit causing my issues with minimal agitation using pyrocat over 1 hour. It turns out the particular film I was using doesn’t like that process.

[Steven Ruttenberg]

OK.

If that's a known effect, I don't understand why the OP asked about it.

- Leigh

Because I didn’t know..When I don’t know about something I ask instead of assuming. Also, our installer did not mention that fact. Why didn’t you know what RO meant?

[pepeguitarra]

Faucet it is 7.56 from RO it is 6.46. Kinda large swing. Faucet is base and RO is acidic. Hmmm

Is your water mostly coming form the Colorado River? Very high in salinity. Maybe that is why you have RO system. RO does not use filters, they use membranes, which is a bit different. Membranes use to last 5 years max 25 years ago. Nowdays, they may last 20 years. They do need cleanup once in a while. You can put some sodium bicarbonate to make it more alkaline. Pepsi and Coke's pH is 2.53. Very acidic. People use Coke to clean the toilet in lieu of Draño.

[Steven Ruttenberg]

Coke is used to clean rust to. Water comes from Salt River. This system has 3 cartridges that is supposed to be replaced at certain times. The tank is 4 gallons I think. One of the cartridges is a membrane. Water first goes thru a water softener that is salt. Was suggested to switch over to potassium. Not sure if being slightly acidic is a big deal though. Guess it depends on the pH level of developer after mixing up. One reason I think it needs replacing is ppm is supposed to be zero but it is at 22ppm. Out of regular tap it is 420ppm. Total salt is 19.8. Almost zero.

[Peter Collins]

Steve--
It's the membrane cartridge which is critical to the final result. The other filters in the 3 filter system need to be changed, too, but if the membrane filter goes, you get unsatisfactory water. Some systems state that 10,000 gals is the trigger for changing, but I think that is optimistic in some western water supplies. (I found Albuquerque water MUCH harder than Southeast MI well water.)

If you are on a city water supply, you might ask what the TDS--total dissolved solids--is in the "finished" water. If you get a chemist technician's help, you might ask water the Specific Conductance is. With this value I might be of some help re life of the membrane filter.

[Steven Ruttenberg]

The water out of my faucet no RO or anything is 442ppm. I can measure the resistance of water and get back to you. I will also call water co and see what they say.

[pepeguitarra]

The water out of my faucet no RO or anything is 442ppm. I can measure the resistance of water and get back to you. I will also call water co and see what they say.

Steve: Water at 0 mg/l or 0 ppm (pure H20) is very corrosive, it has been deprived of all minerales, so it will tend to "suck" or steal minerals from whatever it can. Even at seawater desalination plants, where they can go down to 50ppm, they will blend with other water to raise the mineral content. In Southern California, we get water from the Colorado River at 700ppm, sometimes the water district mix it with water from Northern California (150ppm) to give us a blend 500ppm. When we get 500ppm were are happy. I use water from the refrigerator, which still is at 500ppm, but the carbon activated filter will remove the ammonia or chlorine residual in the water.