GE Merlin Reverse Osmosis Filter Replacement

Replacing the filters on your GE Merlin reverse osmosis system could not be easier, nevertheless we still receive calls asking how to do it. The instruction manual is very informative concerning replacement of the carbon pre-filter and the extended contact carbon post-filter, but we have noticed some events that are not covered in the manual.

For the most part, you should not have to change your membranes but every 3 or 4 years so long as you keep up with your carbon pre-filter replacement. We recommend every 6 months with pre-treatment. In other words, if you have a softener, or if your feed water is less than 10 grains-per-gallon of hardness and your water is not chlorinated, you should be able to get 6 months out of the carbon/sediment pre-filter between changes. If you are not pre-treating your water or your water is chlorinated, it is a good idea to change that filter at least every 4 months. The post-filter (in-line filter) does not need to be replaced every time the carbon pre-filter is but we at Water Value do it anyway.

The first step is to shut off the feed water line to the Merlin RO. If you originally purchased your Merlin RO from Water Value Co., you received a MurLock supply valve. Simply turn it 45 degrees to the off position. Now open your RO faucet and let the water drain out of it. Set the dispenser handle in the upright position so that it stays open. All of the water pressure will now drain out of the RO, but there will still be a considerable amount of water left in the system.

Remove the locking bar on the side of the Merlin (fittings and all) and place it into a bucket. The water in the lines will drain into that. Place the entier Merlin RO into a sink with drains or onto a surface that you don't mind getting wet. The Merlin has a handy "filter wrench" which is the outer support leg. Simply slide it off of the end of the filter/membrane housings. Reverse it and slip it on to the top filter housing. This is the carbon/sediment pre-filter housing. Wrench it counter-clockwise until it spins freely and remove it. The carbon/sediment pre-filter inside should be discarded.

Before unwrapping your new carbon/sediment pre-filter, you should make sure that your hands are clean. GE even recommends wearing latex gloves! Take a tablespoon of chlorine bleach and pour it into the center opening of the carbon/sediment pre-filter sump connection. Use some food grade silicone grease on the o-rings in the pre-filter sump. Unwrap your replacement pre-filter and spread some of the silicone on the seals on each end of that as well. We are talking about a very small amount of silicone grease. Just enough to dampen the rubber seals and o-rings.

Put the pre-filter in place on the sump and screw on the pre-filter housing. Do not use the wrench to tighten this down. Hand tight will suffice. Re-attach the the locking bar and fasten it into place with the retainer. Now place the Merlin RO in its normal position and remove the in-line extended contact carbon filter. Do this by pressing inward on the quick-connect fittings while pulling on the line. The GE Merlin manual recommends cutting off 1/4" from the ends of the line before replacing the new cartridge to insure a leak-proof seal. We have not had need to do this but if your lines come out of the old filter look scored, then it wouldn't hurt to trim the scoring off.

The replacement filter will have a plastic plug in each end. Remove those plugs the same way you removed the water line from the old filter and simply press the lines into the quick-connect fittings.

Now with everything back in place, you need to turn the water back on to the RO and wait a few minutes for it to completely pressure up and purge small air-pockets from the filters and membranes. Open the RO faucet and leave it on. In the past we have noticed quite a bit of fine air (or hydrogen?) bubbles in the water and the TDS was elevated slightly. We let the water run for at least 30 minutes to purge all of the air out of the system. GE does not mention the fine bubble phenomena in their manual but it occurs every time we change filters on the Merlin. Even with the miniscule gas bubbles, the TDS reads near zero after running the product water for about 30 minutes. There is no trace of the bubbles after about 3 days of regular use.

That's about all there is to the filter changes. We have yet to replace membranes but when we do, we'll pass along that experience to you as well. If our customers keep up with their pre-filter changes, that might not occur for a few more years.