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Plumbing in the Home/Residential Water Pressure


The water pressure in my home on the central coast of CA has always (10+ years) been a bit wimpy but sufficient. I don't think a toilet flush has any impact on a shower at the same time.  I thought it was something that I had to live with until a plumber came to take care of a few things around the house.  He measured the pressure as 40 PSI and explained that is outside the acceptable range of 50 - 80 PSI.  He suggested that I call the city PWD, which I did.  

PWD came and measured the pressure again and indicated it was okay (50 PSI) at the main valve in the front of the house but weaker in the back yard.  He suggested that the water softener might be reducing the water pressure in the house.  

Any thoughts?

Thank you, in advance.

Hello Sara,
Actual water pressure is a static reading. It will be the same throughout the system. There is nothing that would make the water pressure different at the front of the house versus the rear of the house so I question the validity of the water company's readings. The service person may have misread the gauge or the gauge may be inaccurate. The plumber's opinion about the water pressure is just that, a personal opinion. The actual plumbing standards designate the acceptable range to be from 40 to 80 psi.  

As far as water pressure to the house, one is at the mercy of the water company system and overall demand. Water pressure will vary throughout the day with the highest usually being in the early hours of the morning when the demand is the lowest and vice a versa.  In any case, there is little you can reasonably do about it without spending a lot of money.

What most residential users equate with poor water pressure is actually poor flow rate because that's what they actually see when they are using the fixtures. Flow rate is measured dynamically in gallons per minute while the fixture is in use.  There is a relationship between pressure and flow rate. Lower pressure will usually equate with a lower flow rate. But it's not exactly a one-to-one relationship. Other factors also have an impact such as condition and age of piping, number of elbows in that particular branch of the water line as well as the actual size of the pipe.  

The PWD person mentioned the water softener. Any in-line device such as a water softener can have an effect on the overall water flow by creating a restriction. Not all water softeners are installed into a piping system the same way. Some people prefer to have soft water on both hot and cold and others only want it on the hot side.

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Dana Bostick


Pretty much any residential plumbing questions. For "item specific" details such as a specific model of fixture, I will need to research and there may not be any useful information available. Note: I live and work in Southern California. We do not, as a rule, use hot water or steam heating systems, oil fired boilers or private water wells so my knowledge in those areas is pretty limited. There are others here on AllExerts that can probably answer those questions better.


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