Life of RO membrane

[hkgar]

I think I need to replace my RO membrane. It is only 2.5 years old and is a s75 GPD from BRS. My TDS after RO is 17 (95% of input TDS). It had been 10, 97%.

[bobbyc366]

Have you flushed it lately? Try that first. Other wise sounds like time to replace.

[hkgar]

I flush it before every use.

I thought they were supposed to go about 6 years

[Jen0221]

Are you still making about 75 gal per day. Most times when the membrane is bad you get bad water production. If tds after pre filters goes up 10% it's time to change them. Sediment and Carbon filters.

[sonoma2nv]

The longevity of an RO membrane greatly depends on feed water conditions, how well the system is maintained and whether the supply is municipal or private well water. Water temperature, pH and the concentration of total dissolved solids of the feed water are parameters that can decrease the life of RO membranes. On most municipal water supplies, reverse osmosis membranes will last at least 2 and often 4 or more years. With private well water that is acidic or rather hard with a high content of dissolved solids, RO membrane life can be significantly reduced and may last only a few months or less. Pre-filters that remove scaling salts or precipitating metal oxides can extend the life of RO membranes. Public water systems utilizing RO treatment often inject special chemicals and use backwashing cycles to reduce membrane fouling.

[azjohnny]

If you do change out the membrane I would suggest a Spectrapure Select Plus ( 99% rejection rate) and a new flow restrictor

[hkgar]

Originally Posted by sonoma2nv

With private well water that is acidic or rather hard with a high content of dissolved solids, RO membrane life can be significantly reduced and may last only a few months or less.

I am on well water so that may explain it.

[hkgar]

Originally Posted by azjohnny

If you do change out the membrane I would suggest a Spectrapure Select Plus ( 99% rejection rate) and a new flow restrictor

I was thinking of the Filmtech, but is the Spectrapure significantly better?

[shermanator]

Originally Posted by hkgar

I was thinking of the Filmtech, but is the Spectrapure significantly better?

You can get pre-tested 99% rejection membranes from Spectrapure for a little more than a 98% (at best) rejection Dow Filmtec. Even if you get the advertised 98% from the Filmtec, you'll use twice as much DI resin with a 98% rejection rate vs 99%.

I have a BRS system and the membrane it came with (Dow Filmtec) was giving me 97% rejection. I switched membranes to Spectrapure and get 99%. That is a huge savings in DI resin.

[mcgyvr]

2.5 years is a perfectly acceptable lifespan on an RO membrane IMO..
2-4 sounds about right..

[Jrhunter0000]

Sounds like its time if you flush it and still get that tds...

[Buckeye Hydro]

The life span you describe is normal.

We have a commercial client with absolutely horrible well water. They don't want to do any pretreatment of the well water (iron or hardness removal is needed), so as a result, their $175 membrane life is about 6 weeks. And they have 8 membranes on the system.

Count your blessings!

Our guaranteed ultra high rejection MAXR membranes have a very high rejection, but like any other membrane are susceptible to fouling/scaling if fed nasty feed water.

Russ

[Buckeye Hydro]

Originally Posted by Jen0221

Are you still making about 75 gal per day. Most times when the membrane is bad you get bad water production. If tds after pre filters goes up 10% it's time to change them. Sediment and Carbon filters.

Just so no one gets confused,

Signs of a membrane gone bad = slowed production (referred to as reduced flux), and or dirtier RO water (reduced rejection).

Don't determine the life on prefilters by checking the effluent TDS - instead monitor the pressure leaving the last prefilter. Even if that never changes, remember carbon blocks have a finite capacity to treat chlorine. That's where the 6-month rule of thumb comes from.

Russ

[hkgar]

Wow. Got a new RO membrane and the TDS before DI is now, drum roll please, 1!
Tds of source water is about 260 and is from a well - after softener. That makes the rejection rate over 99%.

[SpectraPure]

What membrane did you select?

jeremy

[hkgar]

It is the Spectrapure plus 99% rejection rate.

Sorry I didn't mention it on this thread, Jeremy. I have spoken of it on another thread.
http://reefcentral.com/forums/showthread.php?t=2452542

I am confident that any extra cost will without question be saved in DI costs, probably many times over.

[SpectraPure]

Yeah even your old membrane at being 10 TDS when it was "good" was wasting 10 times the amount of DI as you are now. I would get a chlorine test kit from us. This will tell you when to replace the membrane. The carbon block protects the membrane from chlorine. Chlorine damage is typically why membranes rejections lower over time and suffer.

Jeremy

[hkgar]

Not sure I would have chlorine as I have well water. I already have the CO2 test kit and that is a bit high, 12-15

[wolfblue]

The TDS on municipal water can vary over time. I use Filmtec TW30HP-2526 with two 20" carbon and a 20" micron before it. I know one of the pre filters is bad when pressure drops between the pre filters and the boost pump. I know the membrane is bad when the pressure rises between the boost pump, and the membrane and TDS will mirror that.

No water softener before there, I average 5-6 months on a membrane but can go 8-10 months. But for a time I was killing pre filters in as short as a week. Membranes went out in 4-8 weeks. The city water was coming in ugly. Right now I'm 7 months on a membrane, the water is coming in nice.

EDIT: Forgot to mention I test for chlorine after the pre filters but the carbon clogs before passing much CL2

[SpectraPure]

Hkgar,

Yeah typically on a well you would not have chlorine. Sometimes, but not often. depends on what type of well. Anyways you can double to triple your DI life by aerating your RO water, and then pumping it through DI.

Jeremy