The future of water conservation

First, I would like to start with a correction to my February column. I incorrectly stated the vapor pressure of propane as 320 psi. For some reason, the data I discovered quoted the vapor pressure of butane at 68°F, which is to be expected. But, in the same sentence I stated the vapor pressure of propane at 131°F, which yields 320 psi. I don’t know why they listed the vapor pressures of these two fluids at such differing temperatures, but it went unnoticed by me and was pointed out by an engineer in Mississippi, Kirk Rosenhan, who is very knowledgeable about propane. Further research revealed that at 75°F, the vapor pressure of pure propane is about 150°F. I’m told by Mr. Rosenhan that for 70 percent propane—which I believe is the standard product sold—the vapor pressure drops to about 110 psi.

Mr. Rosenhan’s specialty is in fire protection, and he pointed out that during the summer in Mississippi, some propane tanks that are in direct sunlight will pop their relief valves, which poses an interesting challenge for the fire department. Thanks for the clarification, Kirk!

Now, to address the subject at hand. Anyone who has been in this industry for a significant amount of time knows that many of the water conservation and water quality trends that eventually sweep across the country often start in California. This is largely due to our drought and ocean pollution issues. The 1.6 gallon WC started here. The lead free law started here. The SUSMP Act, while a federal act, was first implemented with vigilance here in California. We now have mandated 1.28 gallon WCs, 0.4 gpm public lavs, 2 gpm showers, 1.8 gpm kitchen faucets and 1.5 gpm private lavs. Surely these will soon be mandated nationwide. So, what is on the horizon?

I recently attended a meeting with the Los Angeles Department of Building & Safety (LADB&S), where it was explained that the Mayor of Los Angeles had told the LADB&S that he wants an itemized list of potential water savings measures to be prepared for discussion and possible implementation. Following is a list of what they have proposed so far. Keep in mind that these measures must be discussed and agreed upon by myriad local agencies, and that agreement is far from final. Some of these may become law; some will not. It is essentially a wish list, for lack of a better term.

Also, keep in mind that each of these items takes into consideration differences between new construction versus existing construction, and commercial installations versus residential projects. I will not go into all the details here about this matrix of requirements—especially since these items are far from becoming law in Los Angeles or elsewhere. But, these measures should be on your radar, because some of this legislation might be enacted in your area sometime in the near future.

Item 1 of the proposed code changes for the City of Los Angeles requires separate water meters for outdoor water use. This is a relatively minor issue, especially for new commercial construction. For residential construction, especially existing residential construction, it can get complicated, so the legislation carries thresholds for renovations and expansions that would trigger the requirement, rather than making it sweepingly retroactive.

Item 2 on the list calls for outdoor water use budgets. This has already been enacted by some of the water utilities in Southern California, and does not represent a code change. It is actually a water billing strategy intended to save water, but it is also a revenue generator that penalizes heavy water users while safeguarding the pensions for the respective water districts. The proposed Los Angeles City Code change does not specify what would happen if a water user were to exceed their outdoor water budget, but it would, in theory, govern the design of landscaping projects.

Item 3 addresses the contentious but important subject of hot water delivery. As written, this measure requires the delivery of hot water to plumbing fixtures with a flow of 0.4 gallons of water supply. After debate, the city agreed to increase this number to 0.5 gallons. Ironically, the city also frowns upon the use of 1/2” water pipe, compounding the problem with delivering hot water at this limited volume. If adopted, this requirement will surely complicate hot water circulation systems; require hybrid circulation and heat-traced systems; and increase the cost of hot water delivery. But, in some cases, it would save water.

My commentary: from a behavioral standpoint, I don’t believe that most people wait for hot water delivery to wash their hands at a public lavatory, nor do they wait for hot water at the kitchen sink without using it for another purpose, like utensil prewash. However, people definitely do wait for hot water delivery at the shower, or at the sink when they are shaving.

Item 4 would require that buildings be designed and installed in a graywater-ready fashion, meaning the water closets would have to have a dranage system that is separate from all other fixtures. The connection between the graywater waste and blackwater waste would be outside the building or in an area planned for the future installation of graywater reclamation equipment. Enough said.

Item 5 would require that groundwater from subsoil drainage systems exceeding a currently undetermined daily volume be developed and constructed for beneficial use as approved by the local authorities. While proactive, this item is a wild card due to the vague verbiage of its requirements.

Item 6 simply states the obvious fact that when utility recycled water is available, it shall be used to flush water closets and urinals, and for process or industrial uses. This item is a no-brainer.

Item 7 requires water sub-meters to serve specified tenants, occupancies, equipment and residences for buildings three stories or less. While there is some logic behind this requirement, the fact that it limits itself to buildings three stories or less is quite odd.

Item 8 mandates swimming pool covers for residential occupancies. This seems like a no-brainer and a win-win requirement.

Item 9, the last item, states that where utility reclaimed water is not available, non-potable water shall be generated on-site for “X” percent of non-potable uses from either rainwater, on-site treated graywater, on-site treated blackwater, on-site dewatering, other acceptable sources or a combination thereof. Complicated indeed.

I have intentionally limited my commentary on each of these items, though most of them are worthy of dedicated articles. Given that it has not yet been determined how many of these will in fact become law in Los Angeles, I will suspend that commentary until the jury returns, and we know exactly what we are facing for future designs in Los Angeles, and certainly elsewhere in the future. n


Timothy Allinson is vice president of Engineering at Murray Co., Mechanical Contractors, in Long Beach, Calif. He holds a BSME from Tufts University and an MBA from New York University. He is a professional engineer licensed in both mechanical and fire protection engineering in various states, and he is a LEED-accredited professional. Allinson is a past-president of ASPE, both the New York and Orange County chapters. He can be reached at

Content Type: