RepWars
Intelligence Report
Water Flow Restrictors plus System Pressure Differential equals PROBLEMS !

Federal and State Agencies have enacted legislation which is intended to conserve water. However, these mandates are often forced upon manufacturers, distributors and installers of Plumbing Systems before adequate research has determined how to safely and successfully achieve the proposed goals.

The Problem
A Basic Principle of how water reacts within a domestic water distribution system is that it will follow the path of least resistance. The cold and the hot water piping systems within a building will rarely maintain the same residual pressure due to the variations in their use. This fact is even more prevalent within mid size to large facilities where the systems grow in complexity.

When water "conserving" devices are installed at the outlets of plumbing fixtures, a restriction is introduced at points where the cold and hot water distribution systems intersect. This allows the system that has the greatest pressure to overcome the other. When this occurs, the systems become mixed and permit the system having the highest pressure to flow from the fixtures instead of the one that the user is attempting to receive. Most often, the cold water will have the upper hand. As users attempt to take showers or wash their hands, they will receive lukewarm or cold water from the hot outlet of the fixture. Pressure/temperature balancing shower valves with integral checks will prevent the crossover from occurring at these fixtures, however the majority of faucets do not incorporate check devices so the user of the shower will still be unable to obtain a constant temperature of water to bathe.

Exaggerating The Problem
Every piece of equipment or device installed within the water distribution system that will create a pressure loss can increase the inconvenient and possibly harmful effects that flow restrictors produce. For example, some manufactured thermostatic mixing valve assemblies incorporate a pressure regulator for proper operation. These valves cause a minimum fifteen pound reduction in the hot water system, thus producing an additional fifteen pounds of differential between the cold and hot water systems downstream of their location. This is more than enough to create crossover mixing of the cold into the hot water piping at faucets that have restrictors.

Backflow preventers and water softeners are other common items that are installed at the source of hot water systems, further separating the pressures between the cold and hot systems. Obviously there are numerous ingredients within these two systems that will prevent them from maintaining an equilibrium. Therefore, what is the solution?

Possible Solutions

• Remove the flow restrictors - This seems to solve the problem. However, only the end-users can legally do this. Legislation penalizes manufacturers, distributors, and in some cities installers, for not complying with the water conservation requirements.
  

• Install check stops at each cold and hot water supply to fixtures - This will prevent the cross over from occurring, however, if the pressure differentials are great enough, the user will still only receive all cold or all hot water at the outlet. This also can add significant cost to the project.
  

• Install pressure regulators in branch lines strategically throughout the systems - This may help, but pressure changes downstream of the regulators will not be affected. This can also create problems for fixtures and equipment which require higher pressures for proper operation especially when the building's initial service pressure is low. On a system which incorporates a pressure booster pump, the pump system would need to be sized by taking the pressure regulators into consideration. This solution definitely increases project cost as you can estimate.
  

• Design pressure compensating fixtures - This is a task for the manufacturers which will not be attempted until they are forced to do so. It remains to be seen if and how this could be accomplished without substantially increasing the cost of the fixtures.
  

Summary
Conservation is a Good Idea that can benefit us all if it is achieved properly. Federal and State legislation should not be mandated prematurely since the goals that are being sought may cause opposite results. The verdict concerning low flush toilets is still yet to be determined. Some of the major manufacturers have been able to produce a fixture which can evacuate waste with one flush. However this has taken time, money and is still being researched years after the laws where enacted. Many of the "approved" toilets which are within the lower end of the wholesale price structure still do not sanitarily flush with 1.6 gallons of water, yet they are being installed in many homes and facilities. When a user has to flush a 1.6 gallon fixture two or three times to remove the waste within the bowl, water conservation is not being achieved. The same problem occurs with flow restrictors. When a user has to leave a faucet or shower open for an extended period of time to receive water at the desired temperature, water is being wasted.

Engineers who are employed with some of the major plumbing fixture manufacturers are aware that cross flow can occur through faucets and shower valves when flow restrictors are utilized. Shortly after the requirement for flow restrictors became law, representatives of pressure balancing shower valves used this knowledge to emphasize the importance of having a valve that could compensate for the sudden change in temperatures within a system being exaggerated by flow restrictors.

Funding must be obtained to implement research examining how to restrict fixture flow while at the same time compensating for pressure variations and preventing cross over flow from one system into the other. Until this is done, manufacturers will continue to produce these devices since they are forced to comply with regulations; plumbing engineers will have to attempt to design systems which will be safe and usable and the consumers will have to pay for it all.

The General's Recommendation
Abandon the Concept of Outlet Flow Restriction Altogether. Simply require a maximum domestic water system pressure between 30 to 40 PSI. This pressure would be adequate for all plumbing fixtures. Multi-story buildings could still maintain higher pressures within distribution mains and risers while utilizing regulators on branch lines as required to serve plumbing fixtures.

Another basic principle of how water reacts is the relationship between pressure and flow…Lower Pressure Equals Lower Flow.

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