How to Replace your Toilet Fill Valve with a Fluidmaster 400A

411 plumb If you have a toilet fill valve on your toilet that is not shutting off and is wasting water or, not refilling the tank properly, or making noises in many cases the Fluidmaster 400A is the ideal replacement choice. The 400A fits into more applications, is less expensive, and works better than many other fill valves, making it the ideal replacement choice in many toilet makes and models.

The first thing you need to do is lift off the tank lid and look inside the tank at the fill valve that is there. You need to look at it and make sure that the Fluidmaster 400A will fit in your toilet. The height is adjustable from 9” to 14” and it has a small diameter that usually does not conflict with other toilet tank parts. There are some toilets that have proprietary fill valves that mount in the corner of the tank, some incorporate parts of the flush valve with the fill valve, and some like the Toto G-Max have a special fill valve that has a higher bowl refill rate. Take a look at your fill valve and see if the Fluidmaster 400A appears to be compatible with your toilet. If you have a proprietary fill valve that is very complicated, that usually goes along with “expensive,” I would seek the advice of a plumber, often these valves cannot be replaced with a Fluidmaster 400A.

Common Fill Valves

Most fill valves are quite common, these fill valves or, ballcocks as we call them in the trade are stand alone devices and not tied to other components in the tank. The tank mounting hole is far enough out of the corner of the tank where the Fluidmaster 400A can be installed without interference from the tank or, other components. In some cases The Fluidmaster 400A will work with low profile toilets but in other cases the valve height cannot be adjusted low enough or the operational range is insufficient in which case a proprietary fill valve would be required.

Proprietary Fill Valves

On a few toilets there are designs which require the use of a special fill valve. Sometimes it is a low profile tank where the Fluidmaster 400A cannot be adjusted low enough or, be set to turn on and off in the right range. Other times the manufacturer just puts the hole in the tank to close to a corner or side so the float will hit against the tank not having the clearance it needs to operate. Sometimes they also have unusual tubes that flow water to the bowl at different times triggered by the water level in the tank or, different bowl water level replenishment rates. Many of these fill valves that cannot be replaced by a Fluidmaster 400A. Some of the proprietary fill valves such as the Kohler Float Valve / Fill Valve Kit # 30668, Kohler Toilet Fill Valve / Flush Valve Combination # 30669, older Case toilets, and the American Standard Vent-Away, are in the $2 – 400 price range. A knowledgeable plumber may be able to rebuild them if parts are available.

How To Change A Fill Valve Step By Step

The following steps should be followed to replace the fill valve:

1.)    Shut off the angle stop valve supplying the toilet. This is usually located under the tank on the left side where the supply comes out of the wall or, floor. Flush the toilet and hold the lever so the tank empties as much as possible. Open the tank lid and place it on the floor out of the way. Placing it on the floor ensures it does not fall and break. Tank lids can be quite expensive. Remove the rest of the water from the tank using a sponge, wet vac, or, just be ready to catch the rest of the water with a bucket when the fill valve nut is loosened. Verify that the water is off completely.

2.)    Place a small tray to catch water under the angle stop valve if it comes out of the wall or, if it comes through the floor place rags around the pipe. Using a small adjustable wrench unscrew the nut on the supply line securing it to the angle stop valve. Then using channel lock pliers remove the nut securing the supply line to the old fill valve shank. A small amount of water will come out during this process.

3.)    You are now ready to remove the nut on the old fill valve shank. This is what secures the old fill valve in place. Use channel locks to loosen it. If you have removed all the water nothing will leak but if you haven’t you will need to get a bucket in place to catch the water that is remaining in the tank. Once the nut is removed the old fill valve will lift out of the tank. Unclip the bowl refill tube from the overflow tube and discard the whole assembly.

4.)    Remove the new fill valve and parts from the box. Cut the cone washer from inside of the shank washer. Place the shank washer on the fill valve shank with the smooth side facing up, the bottom of the shank washer has a ridge near the threads that helps the valve line up properly to the hole through the tank.

5.)    Place the new fill valve in the tank to check its height. Look at the picture to the right which you may click on to enlarge and note the critical level mark on the ring of the valve. This ring must be at least 1” above the overflow tube for the valve to work properly. The proper operation of the anti siphon valve depends on this height to protect your drinking water from the toilet tank back-flowing into it. The valve body has 2 pieces that adjust the height by screwing the bottom shank while holding the top of the valve body still. Once the height is correct place the refill tube on the fill valve then place the valve in the tank in a manner that does not conflict with the other parts in the tank and the refill tube points towards the overflow tube. Secure the fill valve in place with the nut provided. Do not over tighten as the tank and or, plastic shank of the fill valve can crack and leak. Make sure that the float does not hit the walls of the tank or the trip lever.

6.)    I recommend using a braided stainless steel supply line of the proper length to connect the water supply. They come in 9”, 12”, & 16” lengths. It is better to have one that is too long and loops rather than have it strained or, kinked. I do not recommend using the Watts Floodsafe closet connectors as I have seen some issues with them. I have seen them false trip and shut off the water supply to the toilet. But far worse I have seen a few that blew apart and caused a tremendous amount of water damage to the home. The connections on the braided stainless steel supplies are rubber gasketed and no Teflon tape or thread sealant is needed.

7.)    At this point remove the cap of the overflow tube if there is one present. Insert the refill tube into the overflow tube and hold it in place with your right hand. While holding the overflow reach down with your left hand and turn on the water supply at the angle stop valve. The tank should fill to the water line marked on the tank or, overflow tube or, if there is no mark to 5/8” below the top of the overflow tube. Turn the water level adjustment screw until the water level is set properly. If the float hits the stops on the adjustment screw without the water level at the correct height the height of the valve is wrong. At this point the valve can no longer be turned to adjust height, so a different method is used. Turn the water back off at the angle stop valve. Pull the locking collar up towards the float. This releases the screw so the valve can be raised or lowered by pushing and pulling. When the correct height is reached push the locking collar back down to again secure the valve in place. Failure to do this will cause the top half of the valve to launch and a resulting geyser. Make sure the collar goes all the way back down into the locked position.

8.)    Once the water level is set correctly pull the refill tube back out of the overflow tube. There are 2 ways to secure the refill tube to the overflow tube. The refill tube must fasten above the overflow tube and direct its flow into the tube. If the refill tube is down inside the overflow tube the water from the tank may siphon into the bowl causing the tank to keep refilling only to leak into the bowl again. The refill tube angle adapter can be used if there is room for the refill tube to feed it without stress or, kinking. Quite often I use the other method which is to remove the metal mounting clip from the angle adapter. The tube then goes over the round part of the metal clip and the clip secures to the overflow in the same manner. Trim the refill tube so it runs nicely without kinks or excessive loops.

9.)    Check for leaks and proper flush. Place the lid back on the tank and cleanup!

As you can see this job is not difficult in most cases, if the fill valve was leaking and was not shutting off, this simple repair will often save you hundreds of dollars on your water bill.

Posted in How To Plumbing Tips, Toilet Repairs Tagged with: , , , , , , , , , , , ,
68 comments on “How to Replace your Toilet Fill Valve with a Fluidmaster 400A
  1. jodi says:

    Hi Redwood! I am wondering how to tell if you need the total repair kit or just the fill valve. My toilet has been making a terrible noise while filling the tank and also takes longer than it used to. Also, I noticed that when I took the tank lid off that the water level was low. I filled it back to the fill line and then flushed. The water did not replenish back to the fill line(I had to add more water). Wondering if there is anything I can to/try myself before calling a plumber. Here is a picture of the parts inside the tank,
    Toilet Tank Parts
    Thanks in advance!!

    • Redwood says:

      Hi Jodi,
      The answer is pretty simple that the “Complete Kit” is almost never needed as when you get to work of that magnitude the parts get somewhat specific to the toilet and the kit almost never has the correct parts. The flapper supplied in the Fluidmaster kits sometimes binds on flush valves causing it to stick open causing it to get a Redwood doesn’t like them rating.

      If you push down in the float lever on the fill valve does The tank fill up? If it does the fill valve may need adjustment with either the screw or the height of the valve to set the correct water level. If the fill valve is not letting water enter the tank, then it should be replaced. Another possible reason for the tank not refilling is if a Watts FloodSafe Supply Line was installed on the toilet supplying it, these supply lines have a valve built into the line that shuts off the water when an excess flow occurs requiring a manual resetting.

      Can you describe the noise the toilet is making when it refills? There are some different ones that toilets make when refilling. A loud jack hammering noise and pulsating flow for instance indicates some type of debris in the water stream that moves with the flowing water alternately blocking the flow, this is usually a loose or, deteriorating washer on the angle stop valve supplying the toilet with water. If this is the case the angle stop valve will need replacement. Many times a valve in this condition will not shut off the flow of water to the toilet.

      Your toilet by what I see will probably need a new Fluidmaster 400A, a Korky #16BP flapper, and a new braided stainless steel closet supply line installed. I would avoid the Watts Floodsafe supply lines as they are subject to nuisance tripping when a home has high water pressure. This article Replacing A Flapper On Kohler Ingenium Flushing System Toilets discusses changing the flapper on a Kohler Toilet which is quite similar to your toilet so it may be helpful.

      I hope you find this helpful,

      • Jodi says:

        Hi Redwood.
        Sorry for the delayed response.
        When I press on the lever it does not refill the tank. It would randomly make a bizarre noise and sound like water rushing when there was no one on the toilet. I went ahead and replaced both the fluidmaster 400a and the flapper. All I can say is THANK YOU. Finally, I am not hearing the noise! It had been going on for about 8 or 9 months and I just put it off. I also went ahead and replaced the same items in the downstairs bathroom due to that toilet running as well. I am greatful that you have this website and are so helpful. Being able to repair something without having to call a plumber is a great feeling. Cheers to you Redwood. Thanks again!

  2. slypickle says:

    We have 1B1 Master Mark IV in all our toilets. One was taking a long time to fill (it was just trickling). My husband replaced it with a Korky Quietfill from Lowes. It flushes louder, fills 3X slower, and uses twice as much water. I notice with the 1B1 that it only uses half the tank of water to flush. If we replace it with a Fluidmaster 400A, which is what you recommend, will the 400A use less water and flush powerfully like the 1B1?

    • Redwood says:

      Hi Sly,
      The Korky Quietfill shouldn’t be filling slower than any other valve, I suspect that since the original valve was filling slowly that there might be a restriction in the water supply. This could be as simple a a washer in an angle stop valve breaking apart and being lodged in the water supply line restricting the flow.

      As for the difference in how much of water in the tank being used with each flush that is not controlled by the fill valve. The amount of water used with each flush would be controlled by the flapper. I suspect that you have a 1.6 gallon per flush toilet and that the flapper has been replaced with a 3.5 gallon per flush flapper. The flappers for 3.5 gallon per flush toilets are designed to stay open until the tank completely drains, while 1.6 gallon per flush flappers have either a timer or float mechanism built into them that has the flapper close once 1.6 gallons or, about 1/2 of the tank has flowed into the bowl during the flush cycle.

      The article “Replacing A Flapper On Kohler Ingenium Flushing System Toilets” here on 411Plumb while it may not be your specific toilet describes a couple of good options for flappers to install on your 1.6 gallon per flush toilet.

      I hope this helps,

  3. Traci says:

    Answered my question perfectly! My refill tube had been knocked out of the overflow tube by water suddenly rushing to fill the tank when the water returned after an outage. Moved it as per your instructions and now my tank fills all the way again. Thank you!

  4. Beverly says:

    Thank you so much for your help . I could not find how to adjust the shank on Fluidmaster 400. You were the only one that explained how. Everything else just said it was adjustable. Again thank you.

  5. Nemo says:


    I stumbled upon your site when googling toilet fill valve.

    The float cup fill valve in my toilet doesn’t shut off even when the water reaches the top of the overfill tube, and the lever is lifted to the top position. When I removed the cap of the fill valve, I didn’t find any sediments around the seal or anywhere in the valve. When the lever is lifted to the top position, a needle is pushed down through the seal in the cap. But I don’t see how that would shut off the water. How does the fill valve actually work? What could be causing the problem here?

    • Redwood says:

      Hi Nemo,
      You can either replace that rubber seal or, depending on the condition of the rest of the fill valve replace the entire fill valve, and supply line as well. I would also consider replacing the flapper unless it has been recently changed.
      Hope this helps,

  6. FPT says:

    I just installed an American Standard replacement toilet. The toilet works fine except that after the tank fills water will periodically continue to come in. I watched and saw the float quickly drop, water come in and the float rise back up (two seconds elapsed?). It almost seemed like pressure from the incoming water caused the float to drop in order to release the water. Does that make sense?



    • Redwood says:

      Hi FPT,
      To me it sounds like water is leaking from the tank into the bowl and the fill valve is refilling the water that leaked. Start by checking the flapper and make sure that it is adjusted properly and that the flapper is not defective.
      Hope this helps,

  7. Rob says:

    Hi I’ve replaced the toilet tank fill valve with a Fluidmaster’s 400A and the water line and the 90 degree valve nothing leaks but I still get a terrible jackhammering sound while the tank fills with water after a flush. What should I do?

    • Redwood says:

      Hi Rob,
      If you are getting a jackhammer sound while water is running my immediate suspicion would be a loose washer on a valve or debris somewhere in the cold water supply feeding the toilet. If it happens when the water shuts off then it would be a different problem. Please advise.

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