We are having trouble with our RO product flow. It is spect. For 2.25gpm and has dropped to just above 1gpm. I have tried cleaning it but have had very little luck. Incoming water temp is ok the product quality is 6us and feed is 360us. I have been using Minnclean AC and Minnclean TF from Minntech. What does everyone else use and where do you get it? thanks

Since it is January and the east and Midwest are below normal temperature as well, your loss of RO output may just be due to much colder water. If this is the case, you must either heat the water somewhat, increase the membrane pressure, or add additional membrane to the system.

If the loss of output is due to fouling or scaling, proper chemical cleaning should restore it. For 15 years I have had good success cleaning thin film composite membranes with generic chemicals. While you may have some type of fouling that will not respond to these chemicals, the likelihood is that they will work.

First take a measurement of water temperature and membrane or pump outlet pressure and record the product water flowrate when these are stable. This represents the dirty membrane condition.

Second you must estimate the total volume of water in the membranes, the mixing tank, and the piping. Let�s say this is 10 gallons or 83 pounds. Typically the acid or caustic concentration needed is 0.5%. This means about 0.42 pounds of chemical are needed.

Clean with acid first. I prefer to use 75% phosphoric acid. It is already liquid, doesn�t have strong fumes, and is very effective. It is used as a concrete etchant and may well be available locally.
Recirculate the reject and product water flows to the chemical tank. Low pump pressure and high flows are desirable. Acid cleaning is usually fast. Recirculate till the temperature rises to about 110oF. Then rinse till product conductivity is say 2X original and measure output.

Acid cleaning removes hardness scale (limestone) and metal oxides. It the softener had a hiccup, acid cleaning will make a dramatic improvement in output. If there isn�t much improvement, scaling wasn�t the problem.

I caustic clean with 0.5% sodium hydroxide with 0.5% sodium EDTA added as a dispersant. The EDTA is especially helpful when the elements are highly fouled but caustic alone works OK. Recirculate the solution to 90oF and then let it sit. An overnight soak is best but may not be possible. Be patient and allow several hours for rinse out. Then test output again.

Caustic cleaning is good at removing most organic and biological fouling. Dirty modules may turn the solution very dark and produce some foam. RO elements on some feed waters may need caustic cleaning frequently.

Operating at a lower water recovery can minimize both fouling and scaling. So if possible increase the reject water flow to drain to minimize cleaning frequency.

Thanks for the info. Where can I purchase the sodium hydroxide and the sodium edta?
Thanks

We have had 2 sets membranes in the course of 8 years become clogged with carbon fines that had somehow gotten past the 5 micron filters. No amount of cleaning would clear this.

At the time, we were using exchange carbon tanks and I suspect the vendor was either using inferior carbon and/or was not back-flushing them correctly. About 18 months ago, this vendor stopped servicing dialysis clinics (kinda makes me wonder).

You might want to pull the membranes out and take a look at them.

I cleaned the Ro last night got it to 1.5gpm. but I notice that there is air in the product water. where would this air becoming from? It was there before I cleaned the unit.