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Thread: Kohler k-401 Mixing valve, Cartridge Repair or Replace?

  1. #1
    DIY Junior Member mrspaceman's Avatar
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    Default Kohler k-401 Mixing valve, Cartridge Repair or Replace?

    I have a shower with a K-401 Mixing valve. Shower used to be hot enough, but now it runs luke warm though the temperature control is max'd out (i have the mixing valve turned all the way hot without the limit stop installed). Hot inlet water temperature is about 130.

    It doesn't look like there is any way to adjust the mixing ratio.

    Any suggestions?

    Thanks!

    http://www.designtool.kohler.com/us/...sp?item=274302
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    Last edited by Terry; 11-18-2012 at 07:31 PM.

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    Master Plumber Redwood's Avatar
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    Is this hot water inlet temp 130 when the shower is flowing? Or does it drop off...

    If it is then you are probably looking at a #78913 thermostatic cartridge...
    I hope you are the original owner and have a warranty... Otherwise you are looking at $234.90...
    Call 1-800-4KOHLER for parts...
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    Last edited by Terry; 11-18-2012 at 07:35 PM.

  3. #3
    DIY Junior Member mrspaceman's Avatar
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    Hard to tell. I measured the inlet temp by turning on the hot water at the bathroom sink. It reads 130 steady.

  4. #4
    DIY Junior Member mrspaceman's Avatar
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    PS - I am the original owner - - whew. Kohler has been great responding to warranty issues. Of course, the fact that this is the second Kohler item (other was a kitchen faucet) that failed is not a good thing. Items were both 7 years old.

  5. #5
    Master Plumber Redwood's Avatar
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    I would say crank up the shower to where it is malfunctioning then while it is flowing check the temperature at the lav faucet.
    Just to make sure it isn't a water heating problem.

    Getting free parts is a good thing!

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    Moderator & Master Plumber hj's Avatar
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    A sticking balancing spool could also limit the amount of hot water flowing from the faucet.

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    Plumber jimbo's Avatar
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    hj....you're slipping! It is a thermostatic model,,,no balance spool.

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    DIY Junior Member jsmabrey's Avatar
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    Default Kohler 401 Mixing Valve Cartridge Repair or Replace?

    Can the Kohler Cartridge #78913 be repaired by a DIYer? The valve stem has only 1/4 rotation with the limit stop removed. Therefore the shower produces only hot and hotter flow. The supply of both hot and cold is within specs. The inlet check/stop valves are open.

    A new cartridge is about $200 which I would like to avoid with a in-house repair. Any advise?

  9. #9
    Moderator & Master Plumber hj's Avatar
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    Cartridges can seldom be "repaired". The normal operation is for the valve to START with cold water and then go to warm and finally hot. IF yours does NOT do that, then something is "stuck" preventing the flow of cold water.
    Licensed residential and commercial plumber

  10. #10
    Plumber jimbo's Avatar
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    Here is the parts diageram for the 401. http://www.kohlerserviceparts.kohler...6b2343d5793084

    Since the cartridge is $230, you might want to get that seal kit 79144 to see if it fixes your issue. There is no possibility of making any internal repair on a thermostatic cartridge.

  11. #11
    DIY Junior Member jsmabrey's Avatar
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    Quote Originally Posted by hj View Post
    Cartridges can seldom be "repaired". The normal operation is for the valve to START with cold water and then go to warm and finally hot. IF yours does NOT do that, then something is "stuck" preventing the flow of cold water.
    Can you address the 1/4 rotation? Does the limited rotation confirm that the cartridge is probably defective? What inside the cartridge could go bad or be obstructed that could not be cleaned? Could I get it back together?

  12. #12
    DIY Junior Member jsmabrey's Avatar
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    Quote Originally Posted by jimbo View Post
    Here is the parts diageram for the 401. http://www.kohlerserviceparts.kohler...6b2343d5793084

    Since the cartridge is $230, you might want to get that seal kit 79144 to see if it fixes your issue. There is no possibility of making any internal repair on a thermostatic cartridge.
    Thanks I've had it out and the screens and o-rings were clean and in good shape.

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    DIY Junior Member marcusk's Avatar
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    Hi jsmabrey,

    I'm having the same problem with my k-401 well the opposite.. I have cold and slightly warm.

    How did you get the cartridge out? Did you use an 11/16 wrench on the stem? Or do you have some kind of larger 1in diameter tool to remove it by the notches on that wider part? Also is it standard thread or reverse?

    The reason I ask is I have cranked on the 11/16 stem quite hard and I can't get it to budge, I don't want to break anything.
    Last edited by marcusk; 11-25-2011 at 01:34 PM.

  14. #14
    DIY Junior Member mrspaceman's Avatar
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    Default Kohler K-401 Mixing Valve

    So here I am exactly two years later with the same problem. I have a Kohler K-401 mixing valve in my shower. Two years ago, the water started running cool to warm, even though the valve was turned to as hot a temperature as possible. I ended up replacing the Kohler Cartridge #78913.

    Two years later, I am having the same problem. I pulled the cartridge, inspected it. It looked like one of the screens moved over the bottom o-ring. I moved the screen back. Replaced the cartridge and now the water is cooler.

    Seems odd to have the same problem again. As Kohler has a life-time warranty, I can replace the cartridge, but maybe there is something else causing the problem? Other than the cartridge there isn't much else in the system. Thoughts?

    Also the cartridge has a very large diameter with a very fine thread. I live in fear of cross threading. If there are tips (other than patience) I'd appreciate it.

  15. #15
    DIY Junior Member tbr220's Avatar
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    I have two of the same mixers, both failed to adjust from full hot. Rather than pay for two new valves I have taken each one out and soaked them in CLR for an hour, rinsed and re installed, both work fine. I have had to do this twice a year for the four years I have lived here to clean out the calcium buildup even though I have a water softener. I remove the screens and o rings first then soak the metal parts in a glass mug then rinse and lube the o rings with silicone grease, re adjust the temp limits and we are back to happy until they get stuck again. Hope this helps.

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