March 13, 2008
Low-Water-Use Toilets Might Be Too Effective
Can low-flow toilets cause problems for sewer lines?
A Pima County program to install the toilets in older neighborhoods at taxpayers' expense is in limbo because of that question. And the answer eventually could change other water- conservation policies as well.The toilets work smoothly and save a little water, most homeowners in the program say. East Siders Jerry Horton, Don Swann and Cathy Kent, for example, called them "perfect,""wonderful" and "awesome."
Only a fraction of the residents complained about having to flush the toilets twice, said the Water Conservation Alliance of Southern Arizona.
But after installing 450 of 1,000 toilets planned for several East Side neighborhoods - in a pilot program that could have been expanded to other areas - the county hasn't ordered any new toilets since late October. The last few already-ordered toilets are now being installed.
The program's future is uncertain due to a paradox at the heart of its seeming success.
Wastewater officials who originally had hoped to reduce flows into the sewers now say they're concerned that the new toilets may reduce flows too much. They're worried that without enough liquids in sewer lines, solids will settle into the lines, causing corrosion, odor and even sewage backups.
The new toilets use 1.6 gallons of water per flush, compared with 3.5 gallons in older toilets.
Homes built in the county since 1992 have been required to use low-flow toilets.
The county decided to try them in some older neighborhoods, too, as a tool to reduce the strain on the sewer system, which has had problems keeping up with growth.
The Regional Wastewater Reclamation Department agreed in 2006 to pay the Water Conservation Alliance, a University of Arizona group, $525,000 for the installations.
But after receiving a consultant's study on the issue last year, the county restricted the areas where such toilets should go. It doesn't want them near a terminal end - the first home on a sewer line - because those areas already don't have much liquid waste. These restrictions are so severe that the program no longer is worth doing, said the Water Conservation Alliance, because it makes no sense to have one home get the toilet while a neighbor doesn't.
"Let's not pretend we're doing conservation when we're not," said Val Little, the alliance's director. "To us, it looks like they didn't have their act together."
The consultant's finding may also hamper conservationists' efforts to help homeowners use more "gray water," such as water from washing machines that could be used to water plants.
The consultant did not totally oppose the use of low-flow toilets and gray water but warned that they could cause problems.
About 19,000 feet of sewer lines in the area have slopes below minimum county standards because they were built many years ago, the report said. Those lines already have or could have problems with solid materials settling and causing odors, clogging and corrosion.
The county already periodically uses potable water to flush sewer lines to move the solids, and flushing would have to increase with use of gray water and low-flow toilets, the report said.
But Little, the Water Conservation Alliance director, said she went through wastewater department records and found that most Sewell-area sewer lines meet county standards, leading her to contend that the study contains inaccurate information.
She said the county hasn't offered evidence of problems in other sewer lines caused by the use of mandatory low-flow toilets in all new homes since 1992.
Regional Wastewater Director Michael Gritzuk acknowledged that the report made mistakes that have been corrected. But sewer-line slopes are only part of the issue, he said.
Sewers in the Sewell area and in other older, flatter parts of Tucson were designed when average indoor home water use was much higher than it is now, he said.
With household water use already declining because of previous replacement of high-use fixtures, "we have now reached the point where there is not enough liquid waste in some portions of our sewer system to carry solids downstream," Gritzuk said.
Originally, the Conservation Alliance had asked the county to also pay for installation of storage tanks and pipes in the East Side homes to allow sprinkling of gray water from washing machines onto yards and shrubs for irrigation. Wastewater officials refused, citing the same concerns about the effects of reduced flows on sewer lines.
East Side resident Horton said he was disappointed that he couldn't get a county-installed tank to store gray water for his lawn and plants.
"We are in a desert. Everyone is trying to conserve," said Horton, a native Tucsonan. "When I heard about the gray water, I thought, 'Wow, we are moving ahead finally as a city,' but now it appears that they don't want to."
Mark Stratton, director of the suburban Metro Water District, sits on the county's Wastewater Advisory Committee and the Water Conservation Alliance Governing Board. He said he appreciates officials' concerns about the effects of low-flow toilets and gray water on sewers, but he said they're overly cautious.
"I questioned the department, saying that since we've had the low- flow-toilet requirement for 15 years or so, 'have you identified new subdivisions built in the past 15 years where solids are a problem?'
"They said, 'We don't know.' They are kind of talking out of both sides of their mouth."
Another wastewater committee member supports the department's position, however.
"I think people think the idea of using low-flow toilets is a fabulous idea, but a lot of ideas get implemented without a lot of practical application," Barbee Hanson said. "You start using these ideas, and they don't work - they need to be fixed."
* Who got the low-flow toilets at county expense? The Sewell, Mittman and Thunderbird neighborhoods, bounded by Speedway on the north, Broadway on the south, Wilmot Road on the east and Craycroft Road on the west.
* If the program continues, who else will get them? The next targeted neighborhood is Harlan Heights, directly north of Speedway in the same area. If successful - and it is now in limbo - the program could be expanded elsewhere.
* Why were those East Side areas chosen first? The county wanted areas whose main sewer lines are running at high capacity. Sewell's line, at 65 percent of capacity, came closest to being full in any built-up neighborhood.
* Pima County wastewater officials hope to meet and try to work out differences on the low-flow-toilet program with the Water Conservation Alliance of Southern Arizona.
* A Tucson City Council task force is meeting until April regarding a proposal to require plumbing for "gray water" in all new homes and water harvesting in new commercial buildings. Its next meeting will be on Feb. 21, from 5 to 7 p.m., at the city's Information Technology Building, 481 W. Paseo Redondo.
* Late this month, the county will issue new standards offering incentives such as shorter times to issue building permits to home builders installing gray-water plumbing in new homes.