Replacing ro/di filters...

Woodstock

Woodstock

The Wand Geek was here. ;)
RS STAFF
How do you know which filters to replace when? :dunno:

Specifically, I have a po4 level of 0.1 ppm coming from my ro/di unit now. Which should I replace?

Hummmm... I should have tested the TDS too... I'll do that tonight....
 
Kensn

Kensn

Well-Known Member
I was thinking when it was time to do mine I would probably just get a whole new unit off EBAY. Didn't think the cost would be much more than all the replacement filters combined. If I was going to change filters it would be all of them. I also have a 100gpd unit, and want to go to a 75gpd unit. The membranes are better in the 75gpd units..
 
oldsaint

oldsaint

Member
IMO I don't think it necessary to replace every filter as soon as you start to have a TDS reading. My ro/di is set up with a 1 micron sediment pre-filter then to a 1/2 micron sediment to a 1 micron carbon to the RO membrane to the DI filter. Maybe I'm missunderstanding your question but it would get very costly if you bought a RO membrane every time you got a TDS reading. As soon as I start reading 1 TDS I backflush the membrane for about 15mins. This usually drops it back down to 0. I go thru 3 sets of sediment/carbon/DI filters before I replace my RO membrane. I also found a refillable DI filter. The resin only cost 19.99 and I can fill it 2 1/2 times.
 
Woodstock

Woodstock

The Wand Geek was here. ;)
RS STAFF
Thanks for chiming in Oldsaint... my specific concern was the po4 level of 0.1 in the output water; which filter removes phosphates?? The DI and Membrane I think... which are the expensive ones. The other prefilters are inexpensive so replacing them early is not an issue. I am debating on whether or not just to buy a new unit like Ken suggested. I haven't had a chance to price filters yet... too busy doing other things right now :D

I will flush the membrane well and test for po4 again and will also test the TDS tonight :)
 
M

mt79

Member
If your RO unit alone is decreasing your TDS by atleast 10 fold it's still good ie. If your tap water is 300 your RO should be 30 or less. If not replace the RO membrane. If your getting PO4 from the DI it's time to replace atleast that filter.
 
M

mt79

Member
I think 90% is the minimal efficiency that should be tolerated. After that your just exhausting DI resin faster and in turn spending more $$. For what it is worth w/ my old RO membrane (18 months of use) I was getting 50+ tds w/ tap at 295. With a brand new membrane I'm only getting 12.
 
Woodstock

Woodstock

The Wand Geek was here. ;)
RS STAFF
I have a 100 gpd membrane. With approx 90 TDS going in, I get zero coming out... or did when it was new. I will retest it tonight...
 
gqjeff

gqjeff

Member
How many stages is your system? Here is a good write up and they have great prices on filters.. This site will be very informative for you. I run a 6 stage and used this filter array and a 75gpd RO membrane with dual DI's. I have 380 coming in and 0 TDS coming out... Get yourself a filmtec 75 gpd RO membrane and it removes 98%.

http://www.airwaterice.com/category/filter.filterarray/

Peace, Jeff
 
Woodstock

Woodstock

The Wand Geek was here. ;)
RS STAFF
I bought mine from Inreef.com when they were in business. It's a 5 stage filter.

Thanks for the link~
 
gqjeff

gqjeff

Member
Your welcome I hope it helps in your decision making.. There is no reason to buy a new system though as this filter array and a new membrane and DI is cheaper...

Peace, Jeff
 
Kensn

Kensn

Well-Known Member
I would at least replace the DI resin. TDS of 1 is pretty good, and as long as the water production is still good, it sounds like you can hold off on a filter change. Might want to change the first sediment one though.
 
C

cheeks69

Wannabe Guru
RS STAFF
HHuuummm I don't replace them or use RO units, does that make me a bad person ? J/K Doni sorry can't be of any help:tears:
 
M

mt79

Member
Kensn said:
12 seems a little high to me..... Maybe I am way off...
Click to expand...
Well I'm starting w/ about 300 tds from the tap, it fluctuates up and down some, and I'm getting 12 after the new RO membrane. That's 96% rejection rate-not bad in my opinion considering it's a 24 gpd unit.The higher the TDS of the tap the higher the TDS of the final product. There are also other factors such as water pressure going through the unit as well as water temp. that affect the efficiency and/or rejection rate of the RO. The final DI stage really "cleans up" the water ie. removes PO4, silicates, etc.
 
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