Moen kitchen faucet low flow repair

(throwing on the cloud for future generations)

I have a single-handle Moen kitchen faucet (it’s a Moen 87787) with sprayer which began to choke up a while ago, with low water pressure in both faucet and sprayer.

Here’s the faucet (which may not have the soap dispenser there)

(part of a Moen diagram)

This is frequently a problem with the diverter, which is the part that controls flow between the faucet and the sprayer. It lives under the spout and not the handle. If your house has old pipes that occasionally flake a bit of rust into the water or hard water that results in mineral or calcium build ups, that’ll clog the diverter and you’ll get no pressure to one, the other, and so on.

(from the Moen exploded parts diagram)

Here’s how you fix it. If you can swing a wrench and don’t have any access problems using it under the sink, it might take an hour to do this. The harder it is to disconnect and reconnect stuff under the sink, the tougher this will be.

Repair instructions
1. Remove the spout. You can do this two ways:
- reverse the installation instructions, leaving the spout body in place
- disconnect the hoses, undo the fastener piece, and pull the whole spout out with assembly and spout body. Then pull the spout assembly off the spout body by unscrewing it.

The first one was a major pain in the ass for me, so I went with the second and it worked well. Then

2. Now within the spout body

You’ll see a small plastic piece, white within the brass spout body. It’ll look like it wants to take a giant hex key.

(I believe that’s a Moen part drawing)

3. Remove the diverter
If you don’t have a giant Allen wrench, you can also take a pair of needle-nose pliers, grab an edge carefully, and rotate it out.

4. Clean the blockage
Examine it and the spout body. If the diverter is the problem, you should pretty clearly see the bits of rust or buildup blocking the holes and water path. Wash out the spout body, then take the diverter and do your worst. If it’s a calcium buildup, you can use vinegar (or whatever your fancy is). You can use water softener if that’s the problem. For me, it was the rust bits, and I just had to brush the whole thing out and replace it.

You can, if want to spend the money, just buy a new diverter from Moen or whoever and have it in hand for easy drop-in replacement.

Then it’s easy.

5. Put the diverter back in the spout body
6. Put the spout assembly back on the spout body
7. (if you took the whole thing out, put it back)
8. Reconnect hoses and fasteners.

Ta da!

Now turn the water back on and test it out. If it was the issue (and you’ll know that at step 4) you should now get the same water pressure as you had before, and the sprayer should work great again.

If it’s not, well, sorry. It’s probably the cartridge. But that’s it for me. Hopefully this will help future generations of people and save them from having to spend a ton of money on kitchen sink repair. And ideally, that particular part wouldn’t be so easy to clog, but I won’t hold my breath for design improvements.

One thought on “Moen kitchen faucet low flow repair

  1. Nick Elias

    this was unbelievably helpful. I live in a rental and the landlords handyman is about 80 and i didn’t want him trying to get under the sink. They probably would have just replaced the faucet. You’ve saved them a bunch of money and me a bunch of aggravation in having to deal with them. Thank you so much. Also, a tip for removing the diverter: a very skinny pair of needle-nose pliers will fit in the teeth of the diverter allowing it to be removed with a little more ease.
    Thank you again.

    Nick

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