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Low Flow Fixture Study

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  • Low Flow Fixture Study

    This is an email I received yesterday:

    As a founding member of the Plumbing Efficiency Research Coalition (PERC), IAPMO would like to share the following message with those interested in water efficiency:
    An important study on Building Drainline Blockages is just short of funding it needs to move forward.

    Here is the issue: Water-efficient fixtures lead to reduced water consumption, and can result in lower drainline and sewer line water flows. This provokes some important questions: Do these reduced flows lead, in turn, to stoppages of waste in building drains? What is the 'tipping point' at which flows can be reduced no further without causing solids to clog the drainline? Does the installation of certain high-efficiency plumbing fixtures contribute to stoppages? If so, are remedies available that can mitigate or prevent drainline stoppages?

    So far, much of the information on this subject is largely anecdotal. However, field failures recently reported in Australia indicate that the emphasis upon aggressive water efficiency practices, fixtures and equipment may have contributed to systemic waste transport-related failures in building drains and sewer lines, costing millions of dollars to repair.

    Will the Australian experiences be repeated in North America? We hope not. Yet, while the drain systems and drought conditions in North America are not necessarily the same as Australia, it is important that the Aussie experiences be considered as a 'wake-up call' to North America.

    What is the Solution? The Plumbing Efficiency Research Coalition (PERC) is undertaking a study that will begin to address those questions noted above by scientifically analyzing the issue of blockages and further evaluating the use of higher volume toilet discharges at intermittent intervals as a way to effectively clear drainlines.

    This is a critical issue that must be resolved, the sooner the better! Lack of answers is currently discouraging many water utilities from running commercial water efficiency programs. It is further stalling the US EPA's plans to develop a WaterSense Label specification for commercial high-efficiency toilets (HETs).

    The good news is that this study will be underway by January, 2012. Due to a generous offer by American Standard Brands to allow the use of its test apparatus, and also due to the generous contributions of others, the study now requires only an additional $50,000.00 in funding to get this important research started. Please consider supporting this effort in whatever way you can. All contributors will be recognized in the Study's Final report. No amount is too small!

    Please contact Mary Ann Dickinson ( at the Alliance for Water Efficiency for further information on contributing funding. Contributions will be tax deductible.
    Learn more about PERC and the study here.

    Coalition Partners: Alliance for Water Efficiency, American Society of Plumbing Engineers, International Code Council, International Association of Plumbing and Mechanical Officials, Plumbing-Heating-Cooling Contractors National Association, and Plumbing Manufacturers International

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    4755 East Philadelphia St., Ontario, CA, 91761

    PERC can be found here:
    Last edited by ToUtahNow; 12-14-2011, 08:56 AM.
    "Somewhere a Village is Missing Twelve Idiots!" - Casey Anthony

    I never lost a cent on the jobs I didn't get!

  • #2
    Re: Low Flow Fixture Study

    Mark, thanks for sharing this. I have known for years that low flow water closets are a huge issue with sewers clogging. Here is what I learned from field experience.

    Buildings where the water closet is the first fixture entering the building drain tend to have more chronic blockages. Homes where the tub/shower, kitchen sink, and laundry enter the building drain before the water closet tend to not clog as often due to the fixtures washing down the line.

    Next thing I noticed is type of water closets that seem to have more issues with clogged building sewers. The power flush water closets, do flush real well and clean the bowl, but since the flush is stretched out, the water slug is stretched out in the building drain and does not carry the waste very far. Some goes for the early 1.6 GPF water closets, they took to long to flush with the 1.6 GPF and the waste would not get carried far enough. Kohler first fixed this issue by glazing the trap way and making the trap way a bit larger (mainly to prevent water closet clogging) this little effort to solve a problem with clogging in the water closet did help carry the waste. Then they manufactures came out with the over sized flappers/flush mechanism. These flush very quick, which in times does not clean the bowl very well, but does create a good slug of water water that carries the waste the furthest.

    Now in my minds eye, the issue is more with the size of the building sewers around here. Its 4" underground, and back in the day with 3.5 GPF water closets they had a large enough amount of water to carry the waste and wet enough area of the 4" pipe. Now with these low flow water closets 1.28 - 1.6 GPF they do not wet enough of the area of the pipe to carry the waste.

    I feel they may need to rewrite the codes to make the building sewers 3" to accommodate the low flow of water in the building drains. As fixtures are added down stream that will help carry the water, then it may need to be increased.

    Ok that there is my thoughts, lets see what the actual study comes out and says.
    Ron Hasil Lic #058-160417
    Ron's Facebook
    A-Archer Sewer & Plumbing specializing in:
    Tankless Water Heaters | Drain and Sewer Cleaning
    Sump and Ejector Pumps | Backflow RPZ Testing


    • #3
      Re: Low Flow Fixture Study

      I think it great some one gets paid for something we all know
      Take one nice little old widow women , with a ft sewer line , and give her a low flow toilet.
      She will have a frequent paper clogs .
      80yr x 150ft divided by 1.5 = slow slurry


      • #4
        Re: Low Flow Fixture Study

        mark, how am i suppose to buy a new jetter when you want to fix the problem.

        we all know on old systems with rough pipe, 1.6gpf and the new 1.28gpf toilets do not carry far enough to properly carry the solids and paper. this is especially true with powder rooms and remote bathrooms that don't get the additional flow and push of other fixtures.

        please don't fix the problem yet, a jetter is an expensive piece of equipment to pay for.

        phoebe it is


        • #5
          Re: Low Flow Fixture Study

          Good stuff Mark, but as long as we have people who want to save the planet with every move we make, low flow water closets will not be going away anytime soon.

          If these people had their way, state of the art "out houses" might start being mandatory.

          I absolutely agree with everything you say though.


          • #6
            Re: Low Flow Fixture Study

            Originally posted by PLUMBER RICK View Post
            mark, how am i suppose to buy a new jetter when you want to fix the problem.

            we all know on old systems with rough pipe, 1.6gpf and the new 1.28gpf toilets do not carry far enough to properly carry the solids and paper. this is especially true with powder rooms and remote bathrooms that don't get the additional flow and push of other fixtures.

            please don't fix the problem yet, a jetter is an expensive piece of equipment to pay for.

            well said.

            My employee always says that Charmin and Cottonnelle PLUS Low-Flow toilets are making us a small fortune.

            this week alone, we have unplugged 5 sewers whose clogs were directly caused by Charmin and 6L toilets.

            I believe that the thickness of the TP is a huge part of the problem. Low Flow toilets do save water, so maybe it's the TP that needs to be regulated. But not until this new jetter is paid off
            Last edited by DukeSewer; 12-13-2011, 11:06 PM.


            • #7
              Re: Low Flow Fixture Study

              Not too long after the 1.6 gallons came out, there was a study of how much water we were actually saving and it was only 11% of our water consumption.

              While people are trying to conserve water...we Plumbers have been busy as hell with repairs.

              Those experts just don't "get it".