What TDS # to change RO/DI membranes?

Hi,

I have been using my SpectraPure 90gpd unit since maybe late January 2010. I make 10g of water a week. I noticed I was getting a TDS reading of 0.01 this past week. I test with my handheld meter so it's a bit more accurate than the in-line ones, I believe the in-lines read 0 still.

When do you know it's time to replace the membranes? Is there a certain TDS # or duration of months, that is the "time to replace" #/duration?

Also, is it easy to change out membranes, I'm not too savvy in that dept, in terms of what membranes I will need to replace and how.

Thanks in advance!

 

Subscribed I'm coming up on membrane change time too, and I'm confused

 

I have heard 1 on your TDS. Membranes are supposed to be good for several years so you may need to flush your unit out and change your cartridges at 1.

 

Sounds like your DI resin is starting to reach the end of it's life. The membrane should be good for a few years, but DI resin is much shorter lived. The more TDS making it through your membrane, the harder the DI resin has to work, and the faster it's ion removing properties are used up. Boosting your pressure is the surest way to lower the TDS after the membrane (there are others) and increasing the life of your DI resin. I would expect a post from AZDesertRat, at some point, going into more detail.

 

I change my DI when I get a TDS reading of 1.
Usually when I do that I am back to 0 for a long time. I change the others when they start to look nasty.

To change them just use the wrench tool that came with it and unscrew the container, take the old one out, put the new one it, screw it back on and flush for a little while then your good to go.

Dont lost the O rings.

 

No doubt AZDesertRat expertise in this field is uncomparable. Spectrapure needs to put him on the payroll as I have purchased all my equipment on his sound advice.........

Kudos to AZDesertRat and spectrapure as I couldn't be more happier with my max cap 90 gpd unit..............

 

+1 on what johnc101 said. AZDesertRat has advised me on many occasions and has been spot-on every time. I'm sure he will chime in on MoJoe's question and provide him with the correct response.

 

Thanks everyone for the great info & advice! I do also hope AZ chimes in as he is the RO/DI Jedi master . From everyones posts it seems I should look into getting a new DI. I'm thinking the 1 reading may be connected to a recent drop in psi as my landlord is doing plumbing work and it dropped my psi from 55 to around 40.

 

It's possible that the plumbing has introduced some fresh dirt in the domestic water system. 40 psi is very low for your water pressure. (plumber)

 

I think you are a little confused, the membrane will go 5-7 years or longer in the Spectrapure systems if you keep up with the 6 month prefilter and carbon block replacements using their suggested replacements and disinfect the system at least annually.

You may be due for a DI replacement soon if you are starting to see a TDS reading. Which system do you have? Which handheld TDS meter do you have? Only the COM-100 reads in tenths and none read in hundredths, so you either have a COM-100(hopefully reading in the ppm NaCl mode) which could be indicating 0.1 or its 001.0 with a normal handheld TDS meter which only read in whole numbers. If its 1 its time to start thinking about a DI resin replacement.

What are your tap water TDS and RO only TDS readings? If you have the MaxCap what is the MaxCap resin reading, the IN on the right hand TDS meter?

There really is no exact number of TDS resin will treat, I have seen it vary from 1500 to over 6000 total TDS per pound (16 oz)of DI resin, the average vertical refillable cartridge holds 20 oz. You say you have had it since late January so that is 8 or so months at 40-50 gallons per month so say 320 to 400 gallons of treated water. It possible its time for DI.

Its easy to replace the DI resin, its the last canister on the right. Shut off the system, unscrew the clear sump on the canister, remove the cartridge and either insert the new cartridge in its place or if you buy bulk resin, unscrew the top of the cartridge and dump the old resin out saving the small foam donut. Rinse the cartridge out, dump most of the new resin in then tap it on the table or counter top several times to pack the resin tightly, add more, tap it again etc until it is full. Stick the donut on top and screw the top back on then insert it in the canister making sure it has the rubber gaskets in place then screw the clear sump back on. Tuen on the system and waste the first 1 gallon of RO/DI water or until it registers 0 TDS again.

Did you take the time to measure your waste rtaio when you first set the system up then trim the flow restrictor according to the provided directions? Often I find prople neglected to do this very important step and they ruin their RO membrane prematurely since it may not be getting flushed at 4:1 like it needs to be. Make sure you do this.

You are late for the prefilter and carbon block replacements if you have not done so already, every 6 months like clockwork. Follow Spectrapures directions and disinfect the system too since it only takes maybe 3 minutes. If your pressure has dropped a quick way to see if it is the incoming pressure or a fouled or plugged prefilter is to temporarily remove the prefilter and see what the pressure is without it, if its near the same the incoming pressure has dropped, if it goes up the filter is in need of replacement.

Spectrapure is still running their sale flyer so all filters and DI resin are still on sale.
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