RO/DI Production Slowing Down

[Sartium]

Hey all, I have a SpectraPure 4 stage 90GPD RO/DI unit that has slowed way down, I can only get about 30 or so gallons out of it in a 24 hour period. The membrane in it is from 11/2014 and I make about 20 gallons a week in it. I did change out the physical filter/carbon block and DI resign about 2 months ago with BRS filters but I just recently noticed the slow down in production. I do have a flush kit on it and I flush the membrane out for about 10 minutes before every use. The pressure gauge on the unit reads around 65 when I am making water so I don't think its a pressure issue. The one thing I worry about is I put the BRS brand of filter/carbon block in when I swapped them out and not the SpectraPure brands. Can this be a possible cause? I didn't notice the slow down right after I replaced the filters but I wasn't really paying too close attention to it.

Any ideas? Do you think its time to replace the membrane already? If the membrane is getting clogged would that show up on the pressure gauge or does that sit in front of the membrane.

thanks!

 

[TheEngineer]

Could be a fouled membrane.

 

[BryanS4]

It's the membrane. I just had the same issue a few weeks ago.

I did a lot of reading and the only other possible problem was the flow restrictor. I replaced that as well and it didn't help.

Membranes were replaced and I was back to normal.

 

[twilliard]

@AZDesertRat !

RO replacement time?

 

[AZDesertRat]

I can't believe you went backwards on filter quality but that is a different subject.
It is common for production to drop some in winter months due to colder water temperature but yours sounds a little excessive.
What is your water temperature, incoming water pressure before the sediment filter and your exact measured waste ratio? What is your tap water TDS, RO only TDS before the DI and final RO/DI TDS? Are you using softened water and if not do you know your water calcium carbonate hardness? Did you disinfect the system when you changed filters?

I hope when you replaced filters you didn't go any larger than 1 micron. Spectrapure systems work so well and last so long for a reason.

 

[twilliard]

Thanks for coming in!

 

[AZDesertRat]

With quality low micron filters a membrane should last 5+ years and if using softened water 10 years. I'm at 8 years now with no drop in production or rejection rate using softened water at 550-650 TDS and I stretch my filter replacements watching headloss and chlorine breakthru.

 

[Sartium]

Thanks for all the quick replies!

@AZDesertRat water temp is 52 F (its cold in Michigan) the TDS at the TAP is 84, the TDS after RO is 2, after the DI stage is 0 TDS. I am on a city water system with no softener. I do not know the the water pressure is at the TAP but the gauge on the unit reads 65 PSI, I dont believe I have the tool to measure this at the tap. I also do not know how to measure the waste ratio? If you can help me with that it would be appreciated!

Also on the BRS filters I am running the Purtrex 1 Micron Sediment Filter and BRS Universal 1 Micron Carbon Block are these really that poor quality compared to the Spectrapure? That's not a issue at all because the cost are very similar I just bought from BRS for the convenience.

Thanks again for the help!

 

[AZDesertRat]

At 52 degrees and 65 psi you should be seeing just over 60 gpd treated water. The only reason I day measure your water pressure at the tap or an outside hose bib is to confirm your pressure gauge reading of 65, gauges sometimes go bad or with RO systems sometimes get screwed in too far and read incorrectly. If your gauge drops to zero when you shut the water off it is probably OK.
To measure the waste ratio you use a kitchen measuring cup and a watch or clock and fill the cup for exactly one minute from the waste line then do the same from the treated line. Should be around 3:1 to 4:1 waste to treated flow ratio.
The filters you have are not bad and you were smart to go with 1 micron or less, for some reason BRS pushes 5 microns which is pretty coarse. I prefer Spectrapure myself because they spend a ton of time testing filters and combinations and even have some built to their specifications so gave the most experience here.

 

[Sartium]

I can measure the waste : production line sometime tomorrow and get back to you, also the gauge does go to zero when the water is off. Again thanks for all the help on this, is this all pointing to the fact that I need a new membrane?

 

[AZDesertRat]

I seriously doubt it. Not with such low tap TDS and being fairly new. I suspect you are going to see the waste is much higher than it needs to be. Did you take the time to check and adjust the waste ratio when you first set the system up and went through the initial flushing? It's on page 8 or do of all the spectrapure owners manuals. In winter it goes up even more since water is not as viscous and doesn't pass through the membrane as easy so goes out the waste. If it was high to begin with it is really high now.

 

[twilliard]

Now I am going to test mine!

 

[AZDesertRat]

The four most important things for RO membrane life and performance are softened or naturally soft water, good prefiltration, the proper waste ratio for your unique water conditions and water pressure. If the waste is too high you are losing pressure down the drain and robbing the membrane so rejection rate and gpd drop. If you waste too little, and many people mistakenly do this, the membrane starts scaling up with solutes until it ruptures and fails. The correct waste ratio is critical and why I like Spectrapure and Buckeye Hydro with their capillary tube flow restrictors that can be trimmed and adjusted by the end user versus a you get what you get restrictor the others use which is rarely correct. RO vendors think we are all dummies and want to sell us a supposedly plug and play system which is rarely correct for our conditions. A few minutes learning and fine tuning your system goes s long way in cost savings from longer component life and in final water quality. Learn your systems ins and outs and you can save money and have better water.

 

[Sartium]

OK I had a chance to measure and here are the numbers
Waste Line = 500Ml
Production Line = 120Ml
This comes out to 4.17 so its really close to the 4:1 ratio in the manual

I dint ever measure it when I first installed the filter (I sure wish I had not for comparison) any other ideas guys?