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Can fill valve cause water to leak into toilet bowl?

orioncyg
orioncyg Member Posts: 20
edited September 29 in Plumbing

I have a Kohler Rialto one piece toilet. I noticed water was leaking into the toilet bowl — I confirmed via the food coloring trick, but it's also quite visible that water is constantly flowing down the walls of the toilet bowl. Note there is no water leaking outside of the toilet.

I contacted Kohler and they said the only way for the water to leak into the bowl is either the flapper or the flush valve gasket is malfunctioning.

I replaced the flapper with a new one but it's still leaking, so perhaps it's the flush valve gasket.

But the constant sound that I'm hearing is coming from the fill valve, so I suspect that might be the issue despite Kohler saying the issue can only be from the flush valve gasket or flapper.

Here's a video for reference:

You can hear the sound of water in the fill valve until I pulled the floater up at which point the sound stops. When I let go of the floater, the sound doesn't return.

Any suggestions?

Comments

  • hot_rod
    hot_rod Member Posts: 25,703


    Can you see the overflow tube, that would indicate if the fill valve is leaking through

    I think that model takes a specific flapper and fill valve

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • mattmia2
    mattmia2 Member Posts: 14,239

    adjust the float or possibly rebuild the ballcock.

    look in the tank, i think you'll see the water level at the top of the overflow tube.

    That is a coast master ballcock, you can get a rebuild kit here

    https://www.danco.com/product/repair-kit-for-coast-ballcocks-2/

  • mattmia2
    mattmia2 Member Posts: 14,239

    here it is at supplyhouse.com

    https://www.supplyhouse.com/Jones-Stephens-T02037-Standard-Large-Head-Kit-with-Three-Screws-For-Coast

    somehow their search didn't find it with something like "coast master rebuild kit"

  • orioncyg
    orioncyg Member Posts: 20

    I attached a pic of another angle I took a couple days ago. actually I don't know where the overflow tube is in this pic?

    Screenshot 2025-09-27 at 11.43.57 PM.png
  • orioncyg
    orioncyg Member Posts: 20

    Wait is the ballcock the same thing as the fill valve?

  • Steamhead
    Steamhead Member Posts: 17,977

    Yes.

    Doesn't look like the water is up to the top of the overflow. Replace the flapper first. If that doesn't solve the problem, it's the flush valve gasket.

    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Consulting
  • STEAM DOCTOR
    STEAM DOCTOR Member Posts: 2,417

    Shut off the shutoff valve. Tank will presumably drain out. If it drains down to flapper level, problem is at the flapper. If it rains down to the level of the gasket below, problem is with the gasket

  • mattmia2
    mattmia2 Member Posts: 14,239

    Was it running in to the bowl when that picture was taken? If it isn't an anti syphon ballcock it will syphon water from the tank in to the bowl if the refill tube is jammed too far in to the overflow tube(or it looks like it goes in to a notch in the china on this model).

    This is the overflow

    image.png

    this is the bowl refill tube

    image.png
  • mattmia2
    mattmia2 Member Posts: 14,239

    if the flush valve gasket is leaking it will still leak after you turn the water off and flush it because the gasket will be under that inch or so of water in the bottom of the tank. That does not look like it is fun to replace. looks like it involves a spud wrench under essentially where the seat is mounted.

  • orioncyg
    orioncyg Member Posts: 20

    Sorry I don't remember what was happening when the pic was taken. Let me check later today

  • orioncyg
    orioncyg Member Posts: 20

    hopefully it's an easy fix, but if not, I may want to just get a new toilet…

  • mikedo
    mikedo Member Posts: 286

    i would recomend just getting a new toilet the new ones are higher and easier to use

  • hot_rod
    hot_rod Member Posts: 25,703

    get a tall, dual flush with a self closing lid. It will change you life! HD has that all in one box.

    Add a bidet seat if you want to get really wild!

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    Grallert
  • mattmia2
    mattmia2 Member Posts: 14,239

    Not a fan of the handicapped toilet that is too far off the floor. The soft closing lid is great though. It has caused me to slam the lid at other people's houses.

    Be prepared for any number of surprises if you pull that toilet that hasn't moved in 50 years.

    Alan (California Radiant) Forbes
  • mattmia2
    mattmia2 Member Posts: 14,239

    But my bet is on the ballcock needing a new seal.

  • orioncyg
    orioncyg Member Posts: 20

    Hey guys. So I did the test that Steam Doctor recommended above, i.e,. "Shut off the shutoff valve. Tank will presumably drain out. If it drains down to flapper level, problem is at the flapper. If it rains down to the level of the gasket below, problem is with the gasket"

    It looks like it drained all the way, so I think it must be with the gasket seal?


    i might try to fix it, but I'm planning on ordering this toto toilet as it's on sale https://slickdeals.net/f/18637624-toto-drake-elongated-toilet-with-1-6-gpf-flush-regular-height-white-free-shipping-cst776csg-01-274-9?src=SDSearchv3&attrsrc=Thread%3AExpired%3AFalse%7CSearch%3AType%3Anormal%7CSearch%3ASort%3Arelevance%7CSearch%3AHideExpired%3Afalse&peid=4c01a7a5-9208-4846-b005-ae57c4740368


    I'm not sure if I have the skills to replace a toilet though so might have to higher a plumber for that — which I'm guessing will cost at least $300 for them to install :(

  • mattmia2
    mattmia2 Member Posts: 14,239
    edited September 28

    you could hire a plumber to replace the flush valve assembly too although you'd have to make sure they do know how to work on one piece toilets, that they don't get confused by what they see. i'd replace the fill valve while i was in there too.(if it was one of the coast brass ones i'd definitely rebuild it, but the plastic ones are nothing special).

    the flush valve is at least plastic so it won't be all frozen together or you can break it apart if it is.

  • mattmia2
    mattmia2 Member Posts: 14,239
    edited September 28

    It looks like either there are some screws in through the flapper seat or it just snaps in

    this is the bottom of it. looks pretty easy to replace. if it is screws get an 18" ling screwdriver

    image.png

    that gasket looks soft and spongy and prone to rotting out after a decade or 2.

  • mikedo
    mikedo Member Posts: 286

    the drake is a great choice im 6' 3' so thats why i prefer the taller one

  • mattmia2
    mattmia2 Member Posts: 14,239

    we've talked you in to spending $800 on a new toilet instead of $20 on a new flush valve, haven't we…

    Alan (California Radiant) Forbes
  • Steamhead
    Steamhead Member Posts: 17,977

    That's a good deal on a good toilet. If you've had problems with that Rialto stopping up, the Drake should eliminate them.

    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Consulting
  • Those Kohler lowboy toilets never impressed me - such a weak flush. And the bowl is way too low for old fellas like me. For them to work properly, you would have to rough-in the water supply directly under the toilet inlet as they require a ½" feed to get the siphon action to work properly.

    The Totos kick butt. "Comfort Height" bowls are just that: Comfortable!

    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
  • orioncyg
    orioncyg Member Posts: 20

    I can try to DIY a toilet replacement but idk if I have the skills. I'll probably be paying around $1k for the toilet + hiring a plumber if I don't DIY.

    Do I need to make sure the footprint of the Rialto matches whatever new toilet I get? I'm hoping it's tile underneath the existing toilet, but I really don't know. if it's not then there's potentailly tile work to be done if the new toilet has a smaller footprint than the old one?

  • Grallert
    Grallert Member Posts: 989

    The toilet should be sitting on tile. Depending on the age of the toilet you'll want to make sure hole distance from the wall is the same. Some older toilets might be 10" to centerline if I recall. As long as the hole lines up with the new toilet it's a pretty easy swap out. That's a pretty heavy toilet.

    Miss Hall's School service mechanic, greenhouse manager, teacher, dog walker and designated driver

  • mattmia2
    mattmia2 Member Posts: 14,239

    The rough in has been standard since like the 20's but there are shorter and longer rough in toilets available for when the construction process screwed up. If it is tile it is likely tile underneath. Sheet viny that has been replaced is a lot more variable, sometimes they don't pull the toilet to install that.

  • orioncyg
    orioncyg Member Posts: 20
    edited October 1

    I'm guessing the Rialto is original to that particular bathroom, which I think was built before the previous owners moved in in the late 90s. I would hope it's sitting on tile, but my house is weird man… it's a 1927 tudor with lots of quirks and weird stuff throughout the house. This bathroom is on the 3rd floor, which I think was previously attic space that was then turned into a primary suite.

    Looks like the weight is over 100 lbs? Good thing I've been hitting the gym :)

  • mattmia2
    mattmia2 Member Posts: 14,239

    the tile worries me less, but the flange could be just a lead pipe formed over the floor and the toilet bolted to the floor itself depending on how old the underlying plumbing is.

  • Intplm.
    Intplm. Member Posts: 2,730

    @orioncyg Your video shows that when you pull up on the float ball, the water stops.

    You need to change the ballcock, AKA the fill valve. You should also check to see if the float ball is rubbing against the side of the tank. If it is, bend the float rod away from the tank wall. If it's rubbing, it will not fully shut the ballcock off.

    Better to replace it with a Fluidmaster 400 series fill valve. That should solve the entire issue. The clear poly tubing on the old one might need a push-fit reducing coupling to adapt the new to the old, and/or the new fill tube that comes with the Fluidmaster should attach to the overflow on the flush valve.

    You mention that you changed the flapper, where the flapper rests on the flush valve…check that there is no disfigurement on the flush valve. If there is, the new flapper will not seat properly.

    Here is a picture of a Fluidmaster fill valve.

    OIP.jpg
    Grallert
  • mattmia2
    mattmia2 Member Posts: 14,239

    they said if they turn the water off the tank drains on its own to below the level of the seat of the flush valve. that means that big fluffy foam gasket under the flush valve is leaking

  • orioncyg
    orioncyg Member Posts: 20

    I was trying to find permits for the bathroom but couldn't find it and not sure if my county's system even documents permits for 90s and earlier.

    It looks like lead pipes were officially banned in the 1970s? I think the Rialto came out after that so hopefully that means they didn't use lead pipes. I also have some suspicion that the owners at the time DIY'ed the bathroom given the (poorly) quality of the tiling that I see.

  • orioncyg
    orioncyg Member Posts: 20

    Indeed it shows that, but I also confirmed that water was draining from below the flapper, so I think it's the flush valve seal (which sits on the bottom surface of the tank) that's leaking, so I'm trying to replace that first and see if it resolves the issue.

    The fill valve probably has other issues though. I feel like if I replace the flush valve seal and it still leaks, then I really should just get a new toilet instead of spending more money and time on parts replacements

  • mattmia2
    mattmia2 Member Posts: 14,239

    Lead supply piping was banned in 1986. Lead waste is still allowed in many places.

    I'd order the rebuild kit for the coast while ordering the flush valve, it is like $3. You could also replace it with a Fluidmaster or Korky, just make sure they can be adjusted short enough for your tank.

  • Steamhead
    Steamhead Member Posts: 17,977
    edited October 1

    @mattmia2 , @Intplm. et al, a standard Fluidmaster will not work in that Rialto.

    Look at the pics again. There is a large plastic tube that disappears into the tank wall. That supplies flush water to the rim of the bowl. A diverter valve at the bottom of the tank feeds water to the rim as the tank level drops. Think of the old Case models and you get the idea.

    ISTR Fluidmaster once marketed an upgrade kit for at least some of these "lowboys" but I don't see it on their site now.

    @orioncyg , go ahead and order the rebuild kit for your current fill valve if it needs repair.

    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Consulting
    mattmia2
  • hot_rod
    hot_rod Member Posts: 25,703

    That Rialto was never a good flushing toilet. They came with a 1/2 FIP x 1/2” compression stop, but you rarely see them installed with the correct stop. They need a large flow to flush properly as @alan mentioned.
    If you did install the 1/2” stop, it was task to get a 1/2” chrome supply tube installed. The stop needed to be perfectly placed.

    It’s not an easy toilet to rebuilt, it needs the correct parts.

    How’s the porcelain finish? If it is worn and dull, yet another reason to replace it.

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Intplm.
    Intplm. Member Posts: 2,730

    The problem is most likely two-fold. One, the ball cock is syphoning, and two, the flush valve is worn. I was speaking for the most part to the fill valve, as the other issue had been covered in earlier posts.

    That said, the toilet tank needs to be rebuilt. @orioncyg There is an etched model number on the inside of the tank. Get those numbers and call them for the replacement parts.