Every six months, it is recommended you change the filters in your RO/DI unit. By keeping up with this necessary maintenance, the production rates will continue at the desired level and the membrane is protected from chlorine damage. While you can visually inspect the filters for discoloration, it would be better to make a note of the date when the filters have been replaced. Typically if you use 125-gallons of RO/DI water per month, it's time to change the filters.
f you prefer to read, see below. :)
In this image, you can see how the sediment filter has changed from white to orange. The carbon filters look relatively new, but should be replaced at the same time.
1) Turn off the water going into the RO/DI system.
I installed an extra ballvalve (available in my shop here) in the cold water (red) line, to make it easier to shut off the water. My connection is behind the washing machine, and honestly I'd rather turn off the water to the entire house than try to get behind the washing machine. Thus this little modification made my life much easier. PLUS if you go on vacation, it might be wise to turn off the water going to the RO unit to avoid a potential disaster.
2) Open one or both valves after the RO unit to release the internal water pressure.
3) Find the housing wrench that came with your unit.
4) Slip wrench around acrylic housing, with the handle pointing to the right.
5) Firm, steady pressure should be used when pulling the handle toward the left. This should be enough to break the seal, without breaking the wrench itself.
6) By hand, unscrew the housing being careful not to spill the water within.
7) Remove the filter, and dispose. Wipe the housing out with paper towels.
8) Make sure the black O-ring is in place before proceeding.
9) Unwrap sediment filter.
10) Insert new filter, making sure it is centered within the base of the housing. Screw back onto the RO/DI unit
Only tighten by hand. Do not use the wrench, this is unnecessary.
To replace the carbon filters, repeat steps 4 - 8 as explained above.
11) Unwrap carbon cartridge.
12) Make sure the flat rubber washers are in place at both ends, and center the cartridge in the housing.
13) Align housing and screw back in place, only hand-tight.
#14) Turn on the water source, and watch as the unit refills.
#15) Check for any leaks, and tighten housing if necessary, hand-tight.
#16) Close ballvalves on the output lines. The unit will pressurize, and shut off automatically. It will be silent at that point. With new filters, as an additional precaution, it would be wise to make 2-3 gallons of water and then dispose. Now it is ready to produce pure water.
How to change the DI cartridge
This is a fully spent (used) DI cartridge. The best way other than looking for color change is to test the water before and afterthe DI for TDS. If the TDS is equal to or higher than the RO water, the DI is done. Many choose to change the DI as soon as any TDS appears on their meter, but anything under 10 is still good to use. I prefer to change it when my meter reads 3-6 TDS.
You will need a new DI cartridge and the plastic wrench.
Following the guidelines as stated above, shut off the water to the unit, and open the ballvalve after the DI to bleed off any pressure. Carefully slip the wrench around the acrylic housing with the handle pointed to the right. With even pressure gently untwist the housing (pulling the handle towards your body and on to the left) from the upper section screwed to the wall. This can be somewhat difficult, so use care not to rip the DI section right off the wall. Steady pressure should loosen it without damaging the mounting bracket.
After removing the old cartridge, rinse out and wipe the canister out with a paper towel. Install the new DI cartridge with the arrow pointing up / the black gasket at the top. Make sure the O-ring is in place, seated in its spot at the base of the canister's threads. (Red arrow in picture below)
Carefully screw the housing back onto the upper section, and tighten well but only hand tight. You do not need to use the plastic wrench. Turn on the water and allow the DI to fill up.
Done. It is ready to use immediately. You do not need to let it run to rinse it out.