How do you know when to change RO filters?

[PaintGuru]

I am getting a bit concerned because I am getting a rather large algae bloom in my established tank. Of course I have been feeding more lately due to added fish, but just to make sure, how does one know when to change the RO filter? And is it hard to change? Thanks.

[Big_Don]

What are your parameters? Have you tested your RO water for phosphates? How long have you had your current filters? The prefilters are pretty easy to change out, but the membrane is a little more of a challenge

- Lara

[PaintGuru]

Of course I don't have any test kits since my system was nice and stable, perhaps I should go out and pick up a few. I've changed the pre-filters before, but I was just curious if there was a tell-tale sign that a filter needed changing. The membrane is quite old, years. I figured it wouldnt be easy :).

[Highlander]

Best bet is to buy a TDS meter. You can pick one up on EBay for about $20. When the cartridges are new you should read 0 PPM. As the cartridges wear out the reading increases.

[PaintGuru]

Ah great, at what level of TDS should one change the membrane?

[The H2O Guru]

Most people change the membrane due to slow production . Membranes as a rule do not wear out .
it is true that the TDS level rises with age . If your TDS is creeping up and you are still mking lots of water it may be time to consider a new membrane . Measure the TDS of the tap water , measure the membrane output . Not water from the D.I. or water from a pressurized storage tank . Take water directly from the membrane and test it . Say your water at the tap is 250 p.p.m and the water from your membrane is 12 p.p.m your membrane is rejecting 95 % of the total disolved solids . No reason to change it .
Let's say your tap water is 250 and your membrane output is 50 p.p.m. then your membrane is rejecting only 80 % of the TDS.
You may want to replace it . If you are using a D.I. post filter you would certainly want to change it .

Remember you can expose a TFC membrane to too much chlorine and ruin it very early on . Keep track of your filter changes . Measure your output and TDS write them down for future reference .

Walter

Originally posted by PaintGuru
Ah great, at what level of TDS should one change the membrane?

[DocHoliday]

I feel your pain Paint. I had battled an algae problem for about 18 months before I realized it was my RO/DI membrain. Anyone no where I can get a TDS meter other than ebay?

BTW, don't be killin' that cool carpet anemone! That frag you traded me, is quite a fast grower.

[AcroSteve]

Check this out. http://www.portagespecialty.com/custom/Misc.html

Bottom of the page. I just ordered one. $22.00 is not too bad for something to keep track of the gallons though your system for you.

Pretty good prices of the other stuff too.

[PaintGuru]

Originally posted by DocHoliday
I feel your pain Paint. I had battled an algae problem for about 18 months before I realized it was my RO/DI membrain. Anyone no where I can get a TDS meter other than ebay?

BTW, don't be killin' that cool carpet anemone! That frag you traded me, is quite a fast grower.

Don't worry, he is doing quite well! It is more of a fish/algae problem at the moment. I just won an auction for one on Ebay for $20, so I will see what that says when I get it. Again, the flow is not bad, but perhaps it would be a good idea to change the 2 prefilters.

[Puffer Daddy]

This may help for the time being...I did it and it droped my ro readings....

http://reefcentral.com/forums/showt...hlight=membrane

[AcroSteve]

I cannot recomend the previously referenced meter.

I got it hooked up and tried it out. It would measure the water usage while I was back flushing the membrane, but the flow while making RO water was not enough to trigger it.

I am sending it back.