Toto CST703 - erratic flushing - need help, please

Discussion in 'Toilet Forum discussions' started by Tinger, Jul 15, 2011.

  1. Tinger

    Tinger New Member

    Messages:
    10
    Location:
    Boston, MA
    Hi all. Hoping you can help me out with a strange toilet situation.

    I have a Toto CST703, 1.6 toilet, which was installed on the first floor of our house. Upstairs, just over this toilet, we have two bathrooms, both of which work just fine.

    This toilet is completely erratic in its flushing. I have replaced the flapper valve several times, and now have a Toto flapper in it THU303, per spec.

    Here’s the symptoms:
    • Erratic flush – from one to the next, may or may not empty the bowl. It will empty one time, and then maybe or maybe not the next, and doesn’t matter if you flush it again immediately or an hour later. Random.
    • Doesn’t matter if you hold the lever down to empty the tank or not. Water level may drop with the flush, but never truly empty
    • The flush almost seems like it’s backing up on itself (splashing), but again, I think that’s the design since others have mentioned splashing for this toilet
    • At the end of the flush cycle, there’s a pretty noticeable series of sounds, almost like gurgling in the vent pipe – low pitch, hollow-sounding, and only on this toilet
    • Upstairs drains and toilets all work fine, and there’s only one roof vent for plumbing, so I assume the vent is OK
    • I reamed out the little jets around the edge of the bowl with a drill bit
    • I can dump bucket after bucket of water down this thing with no backup
    • Erratic any time of day, so I don’t believe it’s water backup in the pipes below the toilet?
    • I’ve snaked this thing with a 6’ snake multiple times.
    • Good plunging doesn’t appear to change its behavior
    • Plugs easily (but I think this is just the toilet design). Plumber put this in, recommending the brand several years ago.
    • House is on septic

    So is this Toto 703 just a poorly functioning toilet design? Or do I have something else going on?

    I’m tempted to yank the toilet and get a Drake or Ultramax, but I’m not sure if I don’t also have a plumbing issue? Venting?

    Any suggestions?

    Thank you!
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,321
    Location:
    New England
    First, ensure that the bowl refill tube is properly pointed down the overflow tube...if not, then the bowl doesn't start at the proper level (this assumes you haven't replaced the fill valve with a non-Toto part or if you did, adjusted it properly). Then, you need to understand that a toilet auger does not always catch things caught in the trap. So, you may still have something in there. Sometimes, the only way to clear it is to remove the toilet and go at it from the bottom. They do make fiber optic snakes that will let you see around the bend from the top, but you probably don't want to spend the money for one unless it's something you would use often. Last (but there are probably other things as well), it's possible when the toilet was set that the wax wasn't centered properly and is partially obstructing the outlet.

    Well, thought of a few other things: if the flange is offset, those can be a source of problems; if a wax ring with a plastic horn was used, on some flanges, it can create problems especially if it is not properly centered or if it is slightly larger than the opening.
    Last edited: Jul 15, 2011
  3. Tinger

    Tinger New Member

    Messages:
    10
    Location:
    Boston, MA
    Thanks.

    Refill tube is fine, and the settings are such that it refills to the right level. Has original flush valve tube, but new fill valve.

    Stuff trapped sounds possible. I haven't pulled a toilet before, but it doesn't seem difficult, especially given this was only installed a few years ago so I should be able to just re-use the hardware?

    It's mounted on 8" tile squares, so would the replacement wax ring need to be a certain type to work with this installation? There's no caulking around the toilet that I can see, so would that mean there's none under the toilet either? I'm willing to try this, but want to have the RIGHT parts so I can do it once...

    Thank you.
  4. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,321
    Location:
    New England
    You're making an asumption re the fill valve. To determine if the fill valve is properly filling the bowl, note the water level in the bowl, then SLOWLY pour some water into the bowl. Once it stops filling, stop, let it settle for a minute or so, then note where the water level is now. If it is higher, the fill valve you bought is not filling the bowl properly, and this will require some of the water from the tank on one cycle to fill it, then it might flush properly on the next, then not well on the next and so on...
  5. Tinger

    Tinger New Member

    Messages:
    10
    Location:
    Boston, MA
    Jim, thanks again for the suggestion. The water levels in the tank and in the bowl are consistent on every flush. The tank fills to the line every time, and the water level always returns to the same point in the bowl. I did your test, and got the same result. Then, I dumped a 3 gal bucket down, and the bowl drains faster than I can pour. And then, of course, it flushed fine 3x in a row after that. Then I added some wads of TP, which also flushed down fine. HOWEVER, next flush - didn't drain again. Bucket dump - seems to clear it. So that would probably mean something stuck in the trapway, or maybe a defective trapway if stuff "sticks" to it and slows down the water flow??

    Any thing about the noises to be concerned about?

    Thanks again.
  6. Terry

    Terry Administrator Staff Member

    Messages:
    15,416
    Location:
    Bothell, Washington
    You have something in the trapway.

    When those things are removed, it will perform again.
    Even something small like plastic Q-Tips can affect performance.
  7. Tinger

    Tinger New Member

    Messages:
    10
    Location:
    Boston, MA
    Thanks. So, as a newbie to pulling a toilet:

    - would you advise disconnecting the tank from the bowl (70lbs combined, which I could certainly lift)
    - any recommendations on a wax ring to get, or consideration on which one?

    tx
  8. Terry

    Terry Administrator Staff Member

    Messages:
    15,416
    Location:
    Bothell, Washington
    Jamie and I assemble toilets before we install them. When we remove a toilet for any reason, we keep them intact.
    Any time you mess with the tank to bowl connection, unless you are reinstalling with all new parts, you're in trouble.

    If the flange is above the floor, you can use one wax ring.
    If the flange is on the 3/4" sub floor, and there is underlayment cut around the flange, I use one regular wax, and then a wax with horn.
    You can get many arguments on this, but suffice it to say, this has worked for 36 years and I'm too old to change.

    The wax rings go on the "floor"
    Then you walk the bowl over and set it down on the wax.
    When we do a pull and reset, we use new bolts and nuts.
    We also replace the supply line at that time. We do things one time, and don't plan on coming back to the same problem. We don't mind working on other parts of the home, but whatever we work on, we do it once.
  9. Tinger

    Tinger New Member

    Messages:
    10
    Location:
    Boston, MA
    Thank you very much for your assistance. Your work philosophy is very sound. One & Done. Wish I could say the same for some of the contractors in my part of the woods!

    Tx
  10. Tinger

    Tinger New Member

    Messages:
    10
    Location:
    Boston, MA
    Just an update on this situation. I decided to call a plumber to check this out. He pulled the toilet and found nothing at all in the trapway. Further investigation found nothing wrong in the drain or venting system. So the suspicion is that this Toto 703 has a defect in the trapway which slows down the exit flow.

    I'm waiting to hear back from the plumber on next steps, but they expect to break it open once we replace it to get the final determination. Don't know if Toto will care, as the unit is 6 years old at this point (too many years of frustration on my part, but thought it was due to it being low flow!)

    I'm leaning towards a 2-piece Drake at this point.

    Thanks
  11. Tinger

    Tinger New Member

    Messages:
    10
    Location:
    Boston, MA
    Thanks to all on this forum. I bought a 2-piece eco Drake II and installed it. Easy (apart from some tricky shimming needed), and all is well. WHAT an improvement!! A really good product.
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