Periodic High Pitch Hum From Toto CST703 Toilet

Discussion in 'Toilet Forum discussions' started by charlesb, May 3, 2014.

  1. charlesb

    charlesb New Member

    Messages:
    13
    Location:
    alabama
    A while back I noticed a slow leak from the toilet tank to the bowl in the guest bath, and got as far as putting it on my ToDo list, but then forgot about it. Then a few days ago we started noticing a periodic high pitched hum coming from somewhere. It lasted only a few seconds each time, and we couldn't figure out where it was coming from. Finally, I did note that it was occurring on a regular 19 minute cycle, so I positioned myself in various rooms at the appointed times, and finally isolated the sound to the toilet in the guest bath

    It's a two piece 1.6 GPM Toto toilet that we purchased in 2003. To my memory it has never been worked on in the 11 years since we bought it. I can't find the model number, but a picture is below, along with the enlarged numbers from the toilet (top two superimposed images) and lid (bottom two superimposed images.
    [​IMG]

    I think I read somewhere on this forum that the flappers are of two types, a blue and a red type, but I can't find that reference now. Here is an image of the tank and flapper, which looks green to me.
    [​IMG]

    It being a Saturday, the plumbing supply store where we bought the toilet is closed, so I guess it will have to wait another couple more days.

    But I did make a video showing the end of the 19 minute cycle. It is at (I don't know why the video displays upside down on YouTube).
    Apparently the slow leak lets the level drop a half inch or so over the 19 minutes, and the fill valve comes on just slightly--causing the high-pitch hum. I don't know if the bubbles coming from the bottom of the fill valve are normal or not. I suspect I have two separate problems with the flapper and the fill valve. Two days later the periodic humming has stopped, but the flapper is still leaking.
    Last edited by a moderator: Aug 26, 2014
  2. Reach4

    Reach4 Well-Known Member

    Messages:
    2,806
    Location:
    IL
    I agree. Start with the appropriate Korky flapper. http://www.korky.com/?p=Products&i=1

    A new fill valve would be in order at the first sign of a further problem with that.
  3. Terry

    Terry Administrator Staff Member

    Messages:
    15,416
    Location:
    Bothell, Washington
    You have an old CST703 toilet that uses a standard 2" flapper designed for a 1.6 gallon flush.
    They also make standard 2" flappers that let out too much water. Be sure to pick up one rated for 1.6 gallons. Any hardware store should carry that.

    If you ever replace the fill valve, look at the Korky MP, which allows adjustment of the bowl fill. Otherwise, replacing with a Fluidmaster 400A is going to seriously overfill the bowl.

    What is that on the bottom of the tank? Gravel?

    [​IMG]
    Last edited: May 7, 2014
  4. wjcandee

    wjcandee Wise One

    Messages:
    1,977
    Location:
    New York, NY
    How does the bowl on this toilet refill without a refill tube from fill valve to overflow riser? Or is that something else that the poster needs to fix?

    Any 2" standard Korky flapper should work; this one is their most-adjustable: http://m.korky.com/product-details.php?product=flapper&num=100

    As Terry points out, this is a reasonably-priced and excellent, easy-to-install fill valve: http://www.lowes.com/pd_336988-868-528MPK_0__?Ntt=528mpk&UserSearch=528mpk&productId=3284948&rpp=32

    You want the one with the silver cap, not the white cap. The silver cap is the MP or MaxPerformance version, the one with the adjustable refill rate.
  5. Reach4

    Reach4 Well-Known Member

    Messages:
    2,806
    Location:
    IL
    Now that you mention it, what is that under the flapper inside the flapper seat?
  6. Terry

    Terry Administrator Staff Member

    Messages:
    15,416
    Location:
    Bothell, Washington
    That tank doesn't use a refill tube. It's kind of odd that way. For some reason, it all works without the refill. I was thinking the MP version, because you could squeeze off the refill to the bowl.
    Either that, or just keep what is there as long as it's working. Going to need the 1.6 GPF 2" flapper though.
  7. appdude

    appdude New Member

    Messages:
    36
    Location:
    Ontario
    Couldn't you just route the refill tube on the new fill valve into the tank?
  8. wjcandee

    wjcandee Wise One

    Messages:
    1,977
    Location:
    New York, NY
    Sure. That's probably why Korky identifies the white-cap 528 as appropriate for this toilet; I guess you just leave off the refill tube and let it spray into the tank. Terry's solution is much more elegant though...

    I wouldn't drop the refill tube into the tank, though. Probably not great for it to be sitting in the tank water, even if this is an anti-siphon valve.

    Original Poster: Just get that 2" Korky flapper at your local hardware store or Lowe's.
    Last edited: May 3, 2014
  9. charlesb

    charlesb New Member

    Messages:
    13
    Location:
    alabama
    Thanks. The dealer I bought it from should be able to supply the correct one. I'll wait on the fill valve and replace it if the hum returns. When I watch it fill, it snaps shut briskly, and I think it is probably OK.

    It does look like gravel, but it's just an artifact from the flash on my camera phone not stopping the water flow.
    I think when we got that toilet the low-volume flush toilets were just becoming common, and Toto was the only company that had figured out how to make them work.
  10. charlesb

    charlesb New Member

    Messages:
    13
    Location:
    alabama
    I did a double-take myself when I looked at the image. I went back and looked again, and there was no gravel in the tank and nothing under the flapper. I guess the camera was using a long shutter speed, and the moving water played tricks on the image.
  11. charlesb

    charlesb New Member

    Messages:
    13
    Location:
    alabama
    I'm glad you mentioned the refill tube, because I noticed its absence too, and was wondering if the original plumber had installed it incorrectly 11 years ago. Glad to learn he had not.
  12. charlesb

    charlesb New Member

    Messages:
    13
    Location:
    alabama
    The leak got worse over the weekend--sometimes accompanied by the loud periodic hum, and sometimes not. I removed the old flapper this morning, and it has an obvious distortion that explains the leak.
    [​IMG]
    I replaced it with a Toto valve THU303 2" flapper, and all is well. The fill valve probably will still have its hum occasionally, but we can tolerate that so long as it isn't every 19 minutes. :)

    The first guy at the plumbing supply store looked at the old flapper and said that any flapper would work. But when I told him that you had said to be sure to get the 2" one for the 1.6 gallon Toto, they called in their expert, and he said I was right. Thanks to all for your help. Without it I probably would have just taken the first one they handed me.

    Now I can get back to working on my 36 year old green tractor with the able assistance of the good folks at the YesterdaysTractor Forum.

    Charles
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