GE Merlin Reverse Osmosis Water Filter Problem Drain Water Stuck On, Never Shutting Off Solution & Other Useful GE Merlin Application Notes
Apparently it is a known problem that the Merlin RO tankless water filter gets stuck so that drain water is constantly running. Supposedly there is a product re-design in the works according to what I have read on the internet by the company that bought the Merlin RO product from GE. Note there is also a ~$500 housing available from a company in England of completely different design that uses the Merlin filters. Having owned a Merlin RO filter for several years I see that I too now have this problem, however I tried a repair I read on the internet and it seems to be working. First off this is a 2 part Merlin design problem. Merlin Design Problem Part One - Unlike other RO filter units that have an externally accessible automatic mechanism that shuts off the drain water when the output water is shut off, the Merlin has this mechanism buried inside where it can not be accessed without cutting the Merlin apart. Not good! Well there is a rubber valve mechanism inside and over time it dries out, and gets stuck easily. What I did after reading about the internet suggested repair was remove the filter from service, take the 3 filters out, spray silicone into Manifold hole of the top housing (about 5 oz), let it set for a few days, while every once in a while I would run hot water thru it. I made a set up which allows me to use a garden hose to the kitchen sink, then with the right adapters, into the Merlin without internal filters. I also put a shut off valve on the Merlin output that allowed me to stop the water flowing out of the Merlin. The idea is that this will create internal pressure to exercise and break free the internal stuck valve. Note that I accidentally was shutting off the drain valve water for a while. This turned out to be a good thing. This started an internal resonating vibration at the right water pressure (adjust the sink water handles to the right pressure until you hear vibrating). That vibration together with the silicone, I believe broke the rubber shut off mechanism free, allowing the silicone to coat it, and operate properly. Once I was able to operate the on off valve to the Merlin output and saw that the internal shut off was now working properly, I ran cold water for a few hours to flush out the excess silicone. This was the part I read from some good Samaritan on the internet. Note that running hot water thru a garden hose may soften the plastic and eventually burst the hose, especially if there are no internal cloth stiffener strands in the hose. This first design flaw seems intentional to force users to purchase a new Merlin Manifold every few years which is a $125 proposition. Not me! If the valve were user accessible like other RO filters, this would be about a $10 fix. Merlin Design Problem Part Two – This design flaw is two part as well. Part one of two, is created because of not having an external storage tank. The external storage tank gives back pressure when the output valve is shut off which pushes back and shuts off the drain water via the internal valve. GE Merlin solves this problem with the post filter. The special Merlin post filter has 2 parts inside. Part one is standard filter material, I assume charcoal, and a second empty space with a plastic bladder about the size of a ping pong ball. That bladder (air bubble) gets squeezed when the output is shut off by the internal water pressure which then acts like a pressurized external water tank. This system does work when new, and if you continue to use the correct Merlin post filters, you will never know the difference. Not me. I cut open my used Merlin post filter to discover that the internal bladder was broken, unable to create any back pressure. Together with not documenting any of this, this seems like another GE Merlin intentional design to force users to buy Merlin replacement post filters. Since I don’t like to be forced to do anything, I designed my own mini external tank and bladder to replace the wimpy Merlin design. I used a standard plastic RO filter housing with a partially inflated rubber glove to act as the bladder. Note that I shut down the third hole with one of those ¼ inch John Guest stopper “T” things. I also put a little piece of plastic tube inside from top to bottom ( angle cut at both ends to keep water flowing) to keep the inflated glove from cutting off the water flow. Come to think of it, you could probably use a partially inflated condom to form the air pocket which gets squeezed down to create the back pressure. Really you just have to keep the air from flowing out of the housing.
Dope! That only took me a few years to figure out. Now because my output water runs slower, and I am filling up a large 150 gallon tank, I tried adding a flow restrictor to the drain water. The idea was that since the output water was going slower, the drain water should be slowed too. Well what I found out was that adding that resistance to drain water (flow restrictor) caused the Merlin RO output to go up to about 50 ppm. Not good. So I took that off. Knowing that lead me to believe that slowing the Merling water output with the ¼” hose, is responsible for getting the output to 2 ppm. This may not seem important but 10 ppm output wears out the DI cartridges much faster than 2 ppm output. A DI cartridge will only remove a certain number of ppm before it does not work any more.
Joe
The Merlin is unfortunately a black box that no one I know of has been willing to cut open and share its workings with the rest of us. Like apparently most others, mine became increasing dysfunctional, eventually producing only a trickle of water through its faucet. Here's what I did to fix it: If you still have the manual, look at the drawing on page 17 and the line that points to the "Prefilter Center Opening". The manifold has 3 large circular connections upon which the filter covers (sumps) are screwed The prefilter sump connection is the one at the end near all the water connections. Page 17 in the Merlin manual contains directions for sanitizing the unit by pouring a small amount of bleach where the prefilter sits in the manifold. At the bottom of this spot there's a hole, like the center of a bulls-eye. The bleach doesn't fall through that hole because there's a rubber stop below. This rubber stop is what gets stuck when your Merlin either leaks water when the faucet is shut off, or dispenses only a trickle when on. When the manifold is functioning properly, the pressure of the water filling the prefilter sump pushes against the stop, opening the seal and allowing water to continue through to the next sump (the one containing the first reverse osmosis filter). When I was troubleshooting, I ran my Merlin with just the prefilter sump connected and neither of the reverse osmosis sumps. Instead of being sprayed with water, I saw only a small amount of water trickling out into the center manifold connection. Even when pushing down with a good deal of force using a round but flat-ended pencil-like stick that I had handy, I couldn't get that stop to move. When a liberal spraying of silicon had no apparent effect, I tried something more drastic. I filled a tea kettle with water and heated it to a boil. With the manifold's sump connections facing up, I poured into the center of the prefilter manifold connection and also completely filled the two RO manifold connections. Because all of the water hose connections were still in place, the hot water had no place to go, and just sat in each. I waited a minute or two and then tried pushing down again. Success! The stopper now went down when pushed and then snapped back when released. Satisfied that it was no longer seized-up, I poured out the water, pushed down on the stopper and sprayed a bunch of silicon spray inside. What mechanism is back there I don't know, but some sort of friction develops over time that keeps the stop from opening or closing completely. I sprayed too through the squarish hole on the side of the center sump connection on the side closest to the prefilter. That squarish hole is where the water exits after flowing past the stop. I hope this makes sense and helps someone else owning a Merlin who's thinking it's beyond repair. To summarize: The part that's sticking is located right where the manual says to put bleach. The stop should give way when pressed and snap back when released. Really hot water unseized mine. Use food grade spray silicon to prevent the stop from seizing in the future. This all should have been in the manual and every new Merlin should have come with a can of food grade silicon spray, along with a stopper "exerciser" tool, for use whenever you change your filters. Oh, well.
ReplyDeleteReally good explanation ! Keep up the great work :)
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