ULV toilets water conservation problematic
ULV toilets water conservation problematic
(OP)
I have heard that the current municipal water conservation fad of requiring ULV (~6 litre) toilet installation and retrofitting is ill-thought through and problematic because it represents the solve-one-problem-at-a-time, linear-thinking for which engineers are frequently criticized. The greater the number of ULV toilets installed, the claim goes, the lower will become the needed hydrostatic head required by existing (& aging) sewer main infrastructures designed for, and requiring the water volumes generated by thousands of conventional 18 litre flush toilets.
So the poop stops moving or requires ad hoc 'solutions' like increased use of pumps to maintain the hydrostatic pressure.
I have heard that this has become such a problem in some jurisdictions that have been so 'successful' in having ULV toilets adopted in large numbers that they have had to issue public advisories to flush the ULV toilets two and three times thus negating any water conservation!
Can anyone direct me to documentation of any jurisdictions where this scenario has occurred and how the problem was handled?
Thank you.
So the poop stops moving or requires ad hoc 'solutions' like increased use of pumps to maintain the hydrostatic pressure.
I have heard that this has become such a problem in some jurisdictions that have been so 'successful' in having ULV toilets adopted in large numbers that they have had to issue public advisories to flush the ULV toilets two and three times thus negating any water conservation!
Can anyone direct me to documentation of any jurisdictions where this scenario has occurred and how the problem was handled?
Thank you.





RE: ULV toilets water conservation problematic
I am not sure how you got on hydrostatic head, that sure doesn't change with reduced flows from ULV's. That said, both pressure and gravity systems are impacted by ULV's in very straight forward predictible ways, its not a big secret to the waste water engineers of the world. With reduced flow comes increased retention times in force mains and decreased velocities in gravity mains. This leads to creating septic waste conditions and nasty solids plugging, and odd wastewater strength profiles depending on diurnal hydraulic conditions.
Short of restoring flows in the piping systems, how to address the problem is simple...rip up all the infractructure and replace it with the correct diameter pipe. That is an expensive proposition, that is why on the surface it appears that people are thinking in linear ways about addressing the problem.
BobPE
BobPE
RE: ULV toilets water conservation problematic
That being said, do we replace all the sewer in the world, OR put more potable water into the existing sewer to make it work. Bob is right, we have to do one or the other.
I vote for slowing population growth so we have enough potable water to put in the large sewers. This will in turn eliminate the need for large mains and wetwells, so low flush toilet can be phased in concurrently with upgraded, smaller conveyance facilities.
By slowing population growth, this problem, and almost all environmental problems become less of an issue. But most people appear to disagree, so I must be off-base.
RE: ULV toilets water conservation problematic
RE: ULV toilets water conservation problematic
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