ph from 9 to 5.0??

[DREW]

I purchased a R/O-DI water filter and I tested my water from the city and ph was off the charts at around 9.5. I just set-up the ro system and I tested the water in the trash can and it comes out at 5.0. Is it common to have that large of a drop in ph. I will run a airpump and heater and mix a little tapwater in the mixture. I'm just playing around with the water chemistry because I just moved into the house and didn't know what to expect. I thought ro's will put the ph at around 7.0?

Thanks
Drew

my RO puts out a ph somewhere between 6.0 and 6.5. From what I hear that is the norm... I also have five stages. Put your RO water in a trashcan and aerate and heat it for 24 hours so the ion exchange can complete itself, then test the ph. It will change over that time most likely. There also must be minerals in the water to stabilize the ph, so do add some tap water back.
brad

[paulmat]

Brad
I have been told that depending on the brand of test kit that some don't accurately read R/O.D/I 'd Ph. I mix with tap water also .the ratio depends on whether your fish are growers or breeders.

Paul

[Ivan]

IMO you cant test pure ro or di water. There is nothing in the water to react to the test kits (or very little)
Ivan