should I change my RO filter?

[Ehgemus]

I have never changed my RO membrane filter, and it is about 2-1/2 years old. The tds after the RO and before the DI is 30 if my meter is right. I change the first three filters every 6-7 months. do you thank it is time to change the RO filter?

 

[spleify]

should I change my RO filter?

Probably time.

Spleify

 

[Ehgemus]

anyone else?

 

[reef_doug]

With 30 TDS out of the membrane you will go through DI quicker which is costly so maybe a good idea.

What's your source TDS at?

Most membranes are around 94% rejection, so you could calculate it and see. IMO... if your source is 500 or less then it's time.

 

[Ehgemus]

my source is 140 -180 tds.
How do you calculate this, I don't know what my RO membrane rejection is and I don't want to take it apart until I change it. just for calculation let say it is 94%

 

[Ehgemus]

so when I buy a new RO filter I should get a 98% rejection ?
also what gpd should I get? does this mean if you get one with 75 gpd you can make 75 gallons in a 24 hour period?

 

[AZDesertRat]

Yes, a 75 GPD will make 75 gallons per day provided you have 50-65 psi (depends on the brand, Dow Filmtec is 50 psi, Applied membranes and GE Water are 65 psi) and 77 degrees F water temperature. if either or both are less the production will be less.

Dow Filmtec 75 GPD seem to be the most popular membrane by far due to their 96-98% efficiency.

Take a look at the top of the page here for a nice calculator which gives you a very accurate estimation of GPD if you know your temperature and pressure:
www.buckeyefieldsupply.com

If your source water is 140-180 TDS and you are getting 30 after RO only then you are only between 78 and 83% efficient right now which is terrible. You are probably eating up DI in a matter of days if you make much water. By comparison a new membrane should give you an RO only TDS of between 3 and 4 if its 96-98% efficient.

 

[Thefilterguys]

Generally we expect two the three years out of a membrane and some membranes perform better and some worse. Unless you have 77 degree tap water expect less for a 75 GPD and more in the range of 50-60 GPD depending on water temp and tap pressure. Filmtec's are considered one of the best performing membranes around and a 75GPD is rated for 98% rejection rate which can very depending on your water conditions. When membranes fail you generally see one of two things either they seize up producing no water or your RO water TDS starts to climb like yours is. I think it's time for a change for you.

Jim

 

[Ehgemus]

Thanks guys!

 

[Icefire]

www.buckeyefieldsupply.com sell 150gpd 98.5% rejection membrane