Servicing your Model 77 Water Filter

Servicing a Model 77 consists mainly of changing its filter cartridge one a year. We have a record of the cartridge that was original equipment in your water filter and can ship it to you if you don’t know its name or model number, but any of the 9.75 x 2.5 cartridges listed in our Cartridge List will fit it. This means you can select from a large number of possible replacements for your unit. If you have the slimline or “Candle” version of Model 77, choose a cartridge from the “Candle Style” section of the same list. Most Model 77s use the KX-1 or KX-PB1 cartridges, which are available in both standard or candle sizes.

To replace the cartridge:

1. Open the filter by screwing the tower off of the base. It comes apart at the base and it's a standard thread pattern that loosens by turning left. It isn't practical to use a wrench on a countertop, so just muscle it apart. If you can’t get it open, the best strategy is to get someone to help so that each person can use both hands. One person holds the base while the other screws off the tower. Sometimes units that have been in use for a long time are hard to open. If you can’t get it, call us at 940-382-3814. We know some tricks that work.

2. While the unit is open, it’s a good idea to lubricate the black O-Ring that’s in the groove of the tower of the filter vessel. Lubricate lightly with silicone grease, if you have some, or Vaseline if you don’t. Silicone is much better and it won’t cause the O-Ring to deteriorate. Lubricating the O-Ring will make the unit come apart much easier when you service it next year, and it’s much less likely to leak.

3. Replace the cartridge. With open-end cartridges like the KX models, there is no up or down. Put it in either way. With Di-Tech cartridges, or with any closed cartridge with a plugged end, it will only fit the right way. If it goes in, you’ve got it right. Don’t force it. With the candle style units, you obviously screw the threaded portion into the only place it will screw in—no way to go wrong on these—but don’t over tighten, just get it snug. With the larger models, it’s very important that the end gaskets don’t fall off or get out of place during installation. The unit won’t work properly if the end gaskets can’t make a tight seal.

4. Reassemble by screwing the vessel back together. If the O-Ring is lubricated, just get it hand tight. Most leaks occur because the O-Ring buckles or is pinched when it is tightened. If it leaks, you can always tighten it a little more.

5. After the unit is reassembled, run it and check for leaks. Allow it to run for a few minutes to rinse the new cartridge before using the water.