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:


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.
 

Jeff Handy

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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.
 

pasadena_commut

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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.
 

Jeff Handy

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If the o ring is greased, it won’t be binding and buckling, or moving around in the groove.
 

pasadena_commut

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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.
 

pasadena_commut

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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.
 

havasu

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Mine is an R/O unit, and has a dedicated air vent, which when clogged, spills out the back of the faucet
 
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