Drainline Transport

With the enactment of the Energy Policy Act of 1992, all water closets (toilets) manufactured in or imported into the United States were required to flush no more than a maximum average of 1.6 US gallons, effective January 1, 1994 for residential models and January 1, 1997 for all models. At that time, concern for drainline transport efficacy was voiced by many in the plumbing trade and those in various professional associations. However, early reporting and research on 1.6 gallon per flush (gpf) water closet models focused primarily on the flush efficacy of the various water closet models on the market in response to significant consumer complaints about poor flush performance. Intermittent and anecdotal complaints of drainline transport problems were not thoroughly researched and largely attributed to older or faulty sanitary drain lines. Since then, water closet manufacturers have made great strides in improving flushing performance.

Recently, the need to find additional efficiencies on water consuming plumbing fixtures has resulted in the creation of voluntary specifications that eliminate another 20% from the flush discharge volume of water closets, bringing consumption down to a maximum average of 1.28 gpf. These toilets are known as High Efficiency Toilets (HETs). Some water closet manufacturers are now voluntarily offering models that flush at 1.0 gpf. This activity has rightfully raised the debate of drainline carry efficacy anew. Many plumbing experts are concerned that we are at or approaching a “tipping point” where a significant number of sanitary waste systems will be affected by drainline transport problems, especially in larger commercial systems that have long horizontal runs to the sewer. Recently, drainline transport problems in Europe and Australia have been reported, further raising concerns.

Looking forward, newer technologies, such as non-water consuming and High Efficiency Urinals (HEUs), lower flow rate faucets and increasingly efficient water consuming appliances will further reduce the amount of water discharged into sanitary waste systems. Grey water reuse systems, a system that collects discharged water from lavatory basins, clothes washers, bathtubs and shower fixtures for reuse, usually for irrigation purposes, is another emerging technology that significantly reduces waste water in residential sanitary drainage systems. Yet, to date, an extensive research project of sufficient scope to be able to determine if significant problems could arise regarding drain line transport has yet to be conducted.

The Plumbing Efficiency Research Coalition (PERC) was founded to develop research projects that will support the development of water efficiency and sustainable plumbing products, systems and practices. Projects are financed through government grants, foundations and private financing.

In 2009, PERC identified Drainline Transport as its first research project. The Drainline Transport of Solid Waste in Buildings, has been released and is now available.

• AWE - Alliance for Water Efficiency
• ASPE - American Society of Plumbing Engineers (added in 2011)
• IAPMO - International Association of Plumbing & Mechanical Officials
• ICC - International Code Council
• PHCC - Plumbing-Heating-Cooling Contractors—National Association
• PMI - Plumbing Manufacturers International