View Full Version : RO slow to work well

03/05/2010, 12:58 PM
I think my RO unit is an Ocean Wave. When it was brand new, I would get about 5 TDS on the output. That increased to about 20. My incoming water measures about 900. I replaced all my filters and my membrane and it is still 20 at the output.

Yesterday when I went to start it up, I flushed the membrane for a while and then started it. I have added a bypass to dump the product water until the TDS comes down. After about 5 minutes, it finally got down to 40 and I started running it through the DI. After several hours running, it got down to a low of about 15.

Is there anything you can think of that might make my RO part work better? Is it more likely that the RO is working fine and the TDS meter is bad? I added the TDS meter later and it isn't the one you sell.

Thanks for the help.

03/23/2010, 11:48 PM
Sorry we were disconnected from our forum for some unknown reason. It would appear at one time your membrane was outperforming and I would expect to see a 98% rejection reading of 18-20 as normal with a tds of 900. I don't think your tds meter is at fault I think you were lucky and may have gotten false expectations from exceptional membrane performance and now things are normal.


03/24/2010, 01:04 PM
How long should the spike last? It appears to talk several minutes to get down to 20 or so on the output water. Is there anything I can do about that?

Right now I have a bypass setup so that I can dump the product water until it gets lower so I don't waste so much resin.

03/24/2010, 03:24 PM
Your tds is extreme at 900 and your really getting about the best you can expect. Your bypass is a good idea so your not getting that huge tds creep dump everytime your membrane starts up. As I said before you were getting spoiled with an outperforming membrane and when you come back to a normal membrane performance its a DI shock.

I should ask as I'm making assumptions that yout running a Filmtec membrane 75 GPD or less?


03/25/2010, 12:09 PM
I bought it from you guys and I'm pretty sure its the 75 GPD.

When I made water yesterday, it only took a minute or two to come down. I wonder if the water is starting to warm up and the cold temperatures compound the problem.

Thanks again - you guys really are the best!

03/25/2010, 10:40 PM
Generally the tds falls down in the first minute but no doubt cold water can have a big impact on membrane performance.