View Full Version : RO/DI unit taking more time to make water

12/29/2011, 06:59 AM
I have a 5 stage 75 gpd unit and what used to take 30 min. to produce 3+ gal, now takes 45 min. TDS meter still reads 000, and hand held TDS meter used for control purposes, confirms the same. I just replaced the pre-filter, the 2 carbon filters, as well as the DI resin. I changed the membrane a little over a year ago. Any ideas/suggestions as to why the unit need more time to produce the 3 gal?
I forgot to add, I use a pressure pump and my psi is around 92 psi while making water. Do I need to replace the membrane? Thank you.

12/29/2011, 07:20 AM
The membrane should last about 3 years....whatever that means since it really varies on how much people use it!

I have noticed that the output decreases as the incomming water temperature gets colder, that may be what you are seeing.

Vinny Kreyling
12/29/2011, 08:23 AM
Cold water definately slows down water production.

12/29/2011, 08:34 AM

12/29/2011, 12:33 PM
A 75 GPD membrane with pressure pump can produce water at a rate of up to 90 GPD. The rate your giving is considerably higher so any drop in water temp can cause noticable reduced production. It is also possible that as your membrane ages production is falling off but a replacement may produce only normal results which would be far less product water. With an overproductive membrane we suggest running it as long as you can.

We look at rejection rate and not production to tell when replacement is needed.


12/29/2011, 02:48 PM
Thanks everyone. I think you all nailed it. My water definitely is much colder this time of year and production started to drop off right about when temperatures began to drop.
Thanks again everyone.