Fluidmaster Flush Valve fill extremely slow (built in flow restrictor).

Users who are viewing this thread


Currently under Chemo Treatment.
Reaction score
Orlando, Florida
Just like to pass on some information. Today at my son's house I replaced the diaphragm on a Fluidmaster 400A flush valve. It was taking about 5 minutes to fill the tank for water was barely flowing. The diaphragm was not the issue. I then tried a new flush valve as I only changed the top half. Save the hassle if disconnecting the water line, removing the stem, emptying water from the tank, etc. That still did not resolve the issue. Looking things over on the unit, I saw a flow restrictor at the bottom of the stem where the water line connects. Well this 12 year old or older American Standard toilet original flush valve had a slightly different flow restrictor. With a long screwdriver coming in from the top, i was able to pop out the old one. As you can see the old one on the left was made of a soft rubber like material that was collapsing under pressure. The new one is made of a plastic material. Inserting the new one resolved the problem. The flow restrictor is like a screw where the water travels along the threads. I assume without one the valve would be very noisy on fill and it probably reduces water hammer on shut off. I've used 400a forever and it is the first time I've seen this or knew of this part. The packaging and specs of the 400a has no mention of it.

Last edited by a moderator:


New Member
Reaction score
Kingsland Tx
My Fluidmaster flush valve is 8 years old and took 5 to 7 minutes to fill tank. Tried cleaning everything but did not help. Replaced the diaphragm which also did not help. Decided that I would just replace the entire unit so I came back to this GREAT site and found this post. I pulled the old unit out. Got my needle nose pliers and pulled the piece out. Reinstalled altered unit and everything works better than it ever has. Granted, probably going to use a little more water. No more use than it gets, should not affect my water bill at all as I never go over the minimum charge anyway AND best of all, it takes less than 30 seconds to fill the tank and yes, it is a little louder but it beats 7 minutes listening to a seeping fill! Really do appreciate this site and its info for us amateurs.

Had to edit this as my statement about using more water is actually dumb. I am only going to use the tank of water regardless of how fast it fills.
Last edited:


Reaction score
I just recently replaced the fill valve in a toilet for my neighbor and she bought a FluidMaster. I too was very disappointed at how long it took to fill the tank (and it was a 1.6 tank). They have low water pressure and it took forever to fill the tank. I took a needle nose pliers and pulled out the flow restrictor and re-installed the fill valve. It fills now at normal speed and there have been no issues. Korky is much better.
Hey, wait a minute.

This is awkward, but...

It looks like you're using an ad blocker. We get it, but (1) terrylove.com can't live without ads, and (2) ad blockers can cause issues with videos and comments. If you'd like to support the site, please allow ads.

If any particular ad is your REASON for blocking ads, please let us know. We might be able to do something about it. Thanks.
I've Disabled AdBlock    No Thanks