Countertop water filter leaks, and then doesn't

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pasadena_commut

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This is super low priority.

We have an old Kenmore 34551 countertop water filter. They don't make them anymore but here is a picture:

https://www.searshometownstores.com/product/Kenmore-34551-Countertop-Water-Filter
It is basically the same as most other cylindrical cartridge housings. The cartridge is sealed top and bottom with rubber to the housing. Water enters the housing on the outside, is forced through the cartridge into its inner space, and then takes a "tunnel" through the casing to the spout. The housing is sealed with an O-ring, which is greased at installation. For the many years we have had this, once the O-ring is seated there was never a leak there, for the year or so until the next cartridge was installed.

Recently after 8 months it has been doing something bizarre. If the unit has not been used for "a while" (>10 minutes) when water goes into it there is a leak at one spot at the juncture of the two parts of the housing, water somehow gets past the O-ring. If it is left on it will continue to leak like that forever. However, if it is turned off, even after just 1 second of leaking, and then turned back on, it does not leak. Not even if left on for several minutes. So something about "water enters with interior at low pressure" allows a leak but "water enters with interior at high pressure" prevents it. Which is really peculiar since the O-ring should be firmly clamped top and bottom by the housing. Other than that it works as it always has.

I know the solution is to take it apart, clean the groove where the O-ring sits, and replace the O-ring, but I'm about 99% sure there will be nothing visibly wrong.

Any idea what would cause this peculiar leak or don't leak behavior???

Thanks.
 
Sounds like you already know the answer, change the o ring.
Clean and grease the o ring channel and o ring.
Exact matching o rings can sometimes be hard to track down.
Sometimes I need to order by measurement and also by eyeball, and sometimes get one size bigger, smaller, thicker, thinner, etc, til it stops leaking.
I have more experience with the whole house type units, but there are many o ring stores online.
 
The threads are not near the O-ring seal. You mean so they won't bind up and keep the housing from tightening all the way? This housing has always been peculiar as tightening things go, because the best seal comes when it is tightened "just enough", which is just hand tight, no tools. Go past that and it will start to leak (not like the strange one in this post, an unconditional leak.) I think when it is just tight enough the O-ring is compressed but still able to slide against the upper and lower services. Beyond that one side or probably both sides of the O-ring stick, and further rotation causes the O-ring to buckle in some manner because of the shear, so that it leaks.
 
I only install high quality water filters.

Junk floods homes....
 
If the o ring is greased, it won’t be binding and buckling, or moving around in the groove.
 
The O-ring was greased. I do not recall the brand but it was a food grade silicone grease.

Whatever this problem was it seems to have fixed itself, at least temporarily, since it has not leaked in the last two days.
 
By "air vent tube" do you mean the spigot? There is only the inlet for the house water and the outlet for the filtered water.
 
Mine is an R/O unit, and has a dedicated air vent, which when clogged, spills out the back of the faucet
 
Trying to change the filter today and it just refuses to stop leaking. It has always been really fussy about how it was tightened, too little or too much and it leaks from one location (the outlet of the thread grooves, I think, as the O-ring is an inch or so up inside the housing.) Same O-ring type as before (10 were purchased together, new one on each change), greased as before, cleaned as before. Took the O-ring out and inspected the groove very carefully. There are tiny partial radial scratches visible in 3 locations, but they must have been there before. The mating surface has no scratches.

I'm wondering now if perhaps it would be best to only grease the exposed side of the O-ring once it is in the groove. My reasoning is that if the O-ring cannot slide easily with respect to the housing, but can slide easily with respect to the mating surface, it will not bunch up. But when it is greased on both sides it can be stretched/deformed with respect to the housing when the mating side happens to have more grip than the housing side, and that causes leaks.

Have not yet tried greasing the plastic threads to see if really cranking it down will solve the issue.
 
I think I figured this out.

First the O-ring was pulled out, wiped off, and soaked it in water for 90 minutes. Supposedly these swell slightly when immersed in water, and a bit more cross section couldn't hurt.

Then the filter was removed and the groove wiped out with a Q tip. The landing surface was left greased. The entry points of the threads on the two pieces were lined up and a piece of tape placed at the outlet on the housing. Screwed it on and achieved 3 full turns and about 1" more and the two pieces wouldn't rotate any more. That is the maximum amount of rotation. It is a limit on the threads, the grease from the landing surface didn't transfer to the lip of the groove, so those did not touch. The O-ring should seal as long as the two pieces rotate within an inch or two of that position.

Unscrewed the two parts, put in the filter, but not the O-ring, aligned as before, and screwed it together. It became very hard to turn, as in more than I could do with my hands at 2 and 3/4 turns. That was about 5" of rotation from the fully closed location. This is well before the O-ring should make contact.

Took it apart again. Greased the O-ring lightly (but not the groove) and pressed it into position. It kept popping out a little. Eventually got it in pretty evenly. Put in the filter. Align as before and screw together. As before it stopped at 2 and 3/4 turn. Use a strap wrench on one side ( with my wife holding it) and both my hands on the other, and twisted the case together until it was 1" short of 3 full turns, 2" short of the end of the range of motion.

Turned on the water. No leaks.

Why is so much force required? I think the problem is that the original filters are no longer available. The replacements I have been using are Pentek CBC-10 (10" x 2.5"). It is nominally the same size as the original, but is not exactly the same product. The filters from Sears had softer rubber on the ends, or slightly thinner rubber, or both, and it would reliably tighten down by hand to a point where the O-ring would seal. The Pentek end pieces are harder and/or thicker, and the two pieces of the case don't close enough with hand tightening (at least with my hands) so that the O-ring seals reliably.

I'll probably be back in a year asking how to get the stuck case apart.
 
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