Basic Toilet Repair:

Toilet Runs Constantly:
Fixing A Mansfield Fill Valve

In This Article:

A Mansfield toilet fill valve is taken apart, the rubber seal disks are cleaned and turned over, and re-assembled.

Related Articles:
Skill Level: 2 (Basic) Time Taken: 1 Hour

By , Editor


This toilet, about 6 years old, ran constantly after being flushed.

This little tube squirts water directly into the bowl. There were a few drips of water coming from this tube.

I could lift up the float (the big blue ball on the right side, in the top photo) about an inch and make the water shut off. This led me to suspect that the fill valve simply needed an adjustment.

Adjusting the fill valve is easy... just turn the screw at the center. When the screw is turned in, the float will shut off the water at a lower level.

But then I realized that the problem was a little more complicated. Regardless of the screw position, the valve still let water pass through. I knew I had to take the fill valve apart and inspect it for wear.

I shut off the water at the supply valve. Then I depressed the float to relieve the water pressure in the line.

The fill valve comes apart easily. I just unscrewed the plastic ring.


The top part was lifted up...

... and the white plastic "button" removed.


The top rubber seal disc was lifted off. There was a fair amount of mineral deposits, primarily iron oxide, on the parts.

There were some plastic flecks floating on the water at the top of the fill tube. These made me suspicious.


I removed the debris. The homeowner recently had the well pressure tank replaced. Possibly some flakes of plastic got dislodged during that repair, and found their way to the toilet.


I removed both rubber seal disks. I tried to rub off the rust, but it would not all come off.

I used Lime-Away bathroom cleaner to remove the rust. It worked well. Note the small dent in the seal, right at the place where the seal meets the fill tube. This probably caused the leak.

Now the absolutely best possible thing to do is run to the store and buy a new seal disk. But this disk is only slightly worn. Sometimes these disks develop a tear that goes all the way through. If it were torn, I would have definitely replaced it.

But I decided to try something I've done before, in hotel maintenance. I just flipped the disk over. The opposite side was fine. I figured it would be a waste of five minutes if it did not work.


I also cleaned the rust from the white plastic parts of the fill valve.

I replaced the two disks and put the top back on. Note that the top has a tab that has to fit into a slot, to ensure proper alignment.


I installed the white plastic ring, and then turned the water back on.


The toilet worked perfectly. I flush-tested it three times to be sure.

I also adjusted the screw so the water level was close to the mark on the inside of the tank.

A Few Thoughts On Toilet Brands:

A few years ago I worked in maintenance at a major Northern Michigan resort. I did a lot of plumbing repairs. They must have had about 200 Mansfield toilets like the one shown above. They probably had a similar number of Kohler toilets, some dating from the mid 1960's.

When you maintain a resort with around 400 rooms, condominiums, and rental houses, you get a good feel for what products work well.

I found the Mansfield toilets to be easy to work on, because they use mostly plastic internal parts that never corrode. Many components can be removed and installed without tools. I have replaced a few seal disks, and a few fill valves. Mansfield's flush valves can be difficult to replace. I remember having to remove the tank from the bowl to replace a flush valve that had cracked.

One good feature of Mansfield's flush valve is that you can flip the lever the other way after flushing, and interrupt the flow of water from tank to bowl. (This is a great feature if the toilet gets plugged and the bowl is about to overflow.) Most flush valves are lifted by a chain, and fall back in place when the water is gone from the tank.

The Kohler toilet mechanism probably experiences fewer breakdowns than the Mansfield. But Mansfield replacement parts are far less expensive, because they are mostly mass-produced plastic parts.



Tools Used:

  • Phillips Screwdriver
  • Very Small Flat Blade Screwdriver
  • Lime Deposit Remover

Materials Used:

  • None, but a new Mansfield seal disk could have been used.


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Copyright © 1999, 2005

Written October 28, 1999
Revised January 12, 2005