RO Vs. Distilled Water

Man, just make sure the water is clean, pure, and not HARD water.

Roseman is right, as usual. Very hard (lots of dissolved minerals, usually limestone) tap water will cause the tank pH to jump up when mixing up a fresh tank or adding water in between tank dumps. You can correct your pH downward with "pHDown" solutions.

RO or distilled water, while nice, isn't all that necessary. I've been running tapwater for the last 10 years. Just have to adjust the tank pH downward after topping up with plain water.

pHDown comes in two flavours; a phosphoric acid based solution for use in flowering (the plants love the extra phosphorus) and a nitric acid based pHDown for vegging plants (breaks down into nitrogen). pHDown is one of the very cheapest solutions you'll buy from a hydro shop. May be available at some discount or hardware stores these days, too.

My dehumidifier puts out about 10 litres of totally mineral and chlorine-free distilled water per day. I sure don't pour the stuff out! It gets recycled back into the res tanks.

Incidentally, chlorine in tapwater won't hurt your plants one bit. If anything, chlorinated water is your friend. It will suppress pathogen growth in your nutrient solution. The chlorine evaporates from open containers of water in about 24 hours, so that's about how long the tank's protection from rampant pathogen growth lasts without your help.

After the chlorine is evaporated, you have to suppress pathogens yourself. I use hydrogen peroxide (H2O2), 50% horticultural grade, at 1ml/litre of tank volume every 3-4 days. Don't use H2O2 with organic nutes.

Great info! Thank you!

I look at it a little different. I figured I had a choice. Spend $150.00 for the Bluelab ph meter or spend $220.00 for a RO system. Guess which one I choose. The difference in the cleanliness of all of the equipment makes mine the wise choice. Of course my tap water is from a well. In case anyone wonders my system can produce 85 gallons of RO water per day in the winter time. When the weather warms up it will produce more. VV

I use hard tap water (pH 8.8, add pH down, and don't have any problems. Even w/ dH2o the pH has to be brought down a little as ~5.7 is the ideal. However, I'm thinking quite seriously about investing in a RO sys - for my plants and also for myself. Vic, which system are you using?

I have a Spectra Pure dual membrane model. Installation was easy. You do need a drain available since there is about a 5 to 1 ratio for waste. I just added some more 1/4" line and tapped into the side of my sewer line. Took less than an hour to install. VV

VV, that's got to make nice drinking water.

If my tapwater had much more minerals than it does- and it clocks a pH8.7 most days- I'd think about an RO system like yours.

I can corroborate ropascope's experience; the water that comes out of my dehumidifier is about pH7.2. Still has to be corrected down, but not as much as my tapwater.

I think I know what you mean. I have a book, Integral Hydroponics written by an Aussie and he has a section dealing with 'perth' water. Kinda skipped that section. You probably know what he is talking about. VV