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bromion 03-16-2006 11:45 PM

RO/DI slow flow
I'm sure this has come up, but I can't find it. I hooked up a RO/DI unit today, and everything appears to be set right, but my flow rate of RO/DI water is extremely slow. It's a 100GPD unit and so far it's producing 1 quart per hour as opposed to the 4 gal/hour it should.

I've flushed the RO membrane and checked all the connections. Any insights? Does it take time to get going? If so, how much?


greenfish 03-17-2006 02:39 AM

Low water pressure or cold temperature are things that can slow it down. I'm not sure what else it could be. You should definately be getting more than that.

bromion 03-17-2006 02:57 AM

It's producing a ratio of DI:waste of 1:24. Would low temp cause that? I understand the ratio should be around 1:4. My tap water is pretty cold, but I'm in Los Angeles not Wisconsin! It ain't freezing. The pressure coming out of the waste is pretty strong when the flush valve is open, though I can't test it directly.

BillyZ 03-17-2006 09:33 AM

I would check the actual temperature if you have a thermometer handy and compare it to the recommended operating temperature given by the manual for your unit.

greenfish 03-17-2006 10:51 AM

RO/DI needs water temperature in the 70's for optimum performance. You might be surprised how much colder your water is than that. I have heard of people tapping a line from both their hot and cold water lines to a "T" connector to help with the temp. There is also the bucket trick as listed in my post here:

You also state that your water pressure is "strong" but do you know what it is? 50-60psi is where it should be ideally. You can buy a water pressure gauge at you local hardware store for like 10 bucks. Hook it up anywhere (a garden hose connector) to measure the water pressure in your house. If you pressure is really low, you can get a pump to assist your RO/DI.

If the TDS of your incoming tap water is really high I would think that could be a factor too.

seaham358 03-17-2006 05:52 PM

Its possible you got a bad membrane, I have heard of people getting them before.
Cold water will not slow it down that much.. I ran my unit on cold tap water from my well and with pressure that was 50 on the high and 35 on the low end and it worked well.
TDS readings are not going to effect the out flow that much, my friend had a 700 TDS and he could make water, he would burn through resin in no time...
I would call the dealer you got it from and see what thye say, my guess is membrane or something is hooked pu wrong.
A booster pump is a great add on for the ro/di unit.

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