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Thread: toilet drain pitch?

  1. #1
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    Default toilet drain pitch?

    November 1963, on the day President Kennedy was shot, we were moving into our present house built in 1929. My wife wanted a lavatory on the first floor, so I made one. The 4" copper drain is 11.5 feet from where I ran it into the cast iron stack pipe with a saddle. The old toilet, bought then, worked okay, but later was replaced with a water saver that needed a plunger close by.

    About 15 years ago, I drove over to Canada and bought two Kohler 3.5 gallon toilets, one for upstairs and one for the lavatory. The one in the lavatory flushes okay, but often the least bit of toilet paper comes back up. I was told that I have too much pitch in the drain which is about 3.5" per 4' .

    I'm about to begin a remodel, and I wonder if replacing the copper drain with pvc, less pitch, would help any. I was told that the water is escaping too quickly. The lavatory sink enters the 4" drain, going directly into the 90 degree elbow below the toilet. I have an air admittance valve in the sink cabinet, and have had no problem with the trap getting sucked out. But, if I were to reduce the pitch, I would have to make a longer vertical drop between the toilet and the 90 degree elbow below it. Seems to me that this would be worse than the pitch I currently have.

    Should I replace the drain as I described or just leave things as they are? I did read the posts about toilet paper problems, and mine began just several months ago.The upstairs Kohler hooked up directly to the stack doesn't have the problem though.

  2. #2
    Retired Defense Industry Engineer jadnashua's Avatar
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    As long as you have at least the MINIMUM pitch, there is no such thing as a MAXIMUM pitch. Kohler toilets generally get lousy marks for operation...good ones for looks, but I'll take operation over looks (and others can provide both). All objects 'fall' at the same rate. There's more friction on the solids, but it is normal for them to just get moved along on the next flush.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  3. #3
    Forum Admin, Expert Plumber Terry's Avatar
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    Jim's right,
    You either need to snake out the bowl you have, or replace it.
    The Kohler 3.5 was never that good.

    The new performance 1.6 toilets are much better.
    It's too bad you drove to Canada for toilets.

    I'm in the Seattle area, and Canadians are driving South to buy Toto toilets from me.

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    Moderator & Master Plumber hj's Avatar
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    Default toilet

    The fact that you connected the toilet to the stack with a saddle tells us OODLES about your plumbing knowledge. ALL the flushing action of a toilet comes from its design. In certain cases excessive pitch, and/or lack of a proper vent will make it work better, but NEVER worse. You have a TOILET problem, not a drain problem, but without being there we cannot tell you what it is.

  5. #5
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    jadnashua: It was a plumber who told me that excessive pitch could cause the water to flow faster than the solids, causing them to clog. Since I'm going to move the toilet slightly and replace the copper with PVC, I thought it wise to inquire about the pitch. Thanks for setting the matter straight.

    Terry: With all due respect. Your site refers to the water usage laws of 1992 which mandated water saving toilets before good technology was available. Today, Canadians might be flocking to Seattle to buy Totos, but in 1994 people here ware looking for something that would flush. The Canadian plumbing supply where I bought the Kohlers was selling a couple dozen a month to Americans. In 1994, the only Toto I knew of was a dog from Kansas.

    hj: I thought this was a DIY forum where people without OODLES of plumbing knowledge might get some advice. Actually, I have TWO saddles on the stack pipe. One is for the lavatory on the first floor, and the other for the sink and washer in the basement. They've been working just fine for the 46 years since I installed them. May the code enforcers not condemn me to life imprisonment in a septic tank. As to having a toilet problem, I don't think so. No turd has ever won an argument with either of these Kohlers. My inquiry was about toilet paper sometimes not flushing properly. After reading the great toilet paper poll, it seems that lots of people have the problem.

  6. #6
    Forum Admin, Expert Plumber Terry's Avatar
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    When ever I go to Canada, Whistler mainly to go skiiing, they have TOTO toilets where I stay, The Crystal Inn.
    I sold 30 of the CST744SL Drakes to a B&B on Vancouver Island.

    The 3.5 gallon Kohler toilets were never that good.

    Drake 800 grams by Veritech Video
    Last edited by Terry; 11-08-2009 at 08:47 AM.

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    Plumber jimbo's Avatar
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    I can't quote sources, but I seem to recall that enough research has been done to debunk the idea that water will outrun solids on a slope. That issue is certainly talked about, but the 3.5 gallon toilets were an interim design, and most were nothing to brag about in terms of flush performance.

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