Re: Whole house water pressure
Posted by Philip Mathew on May 01, 2004 at 19:25:04:
In response to Re: Whole house water pressure
: : A plumber recently told me our water pressure from the street is too high at 81 psi. He attached a valve to an outside faucet to measure it--I saw the reading myself.
: : We just moved into this house, so we don't know the plumbing history. How do I know this guy is not just trying to rip us off?
: : If it is too high, how do we fix it?
: : thanks.

:
: There is NO SUCH THING as "nomal pressure"

: I'm from New York and to answer it from NYC stand point I would figure the following.

: Flow rate would depend on the fixture Units (FU) needed. A FU is based on 7.48 gallons. A Flushometer would require much more GPM's than a tank and bowl.

: You would also have to size this piping besides the GPM required BUT you must take velocity into consideration as you certainly do not want to cause a premature piping failure due to erosion (normally no more than 8 FPS) as this could also cause hydraulic shock (water hammer) and noisy system. (You may want to contact the Copper Development Association for their recommendations.)

:
: When using a graph you also should show friction losses through pipe and fittings (developed length) & consider the height factor. For pressure if your talking just hydrostatic you take the constant .434 x the height. This will give you no flow conditions. To figure the pressure required to elevate the water you take 2.31 x the incoming pressure to give you the height this water can reach BUT you still have to read the manufactures specifications as per friction loss per fitting and Then you must add into this pressure the REQUIRED min. press for the device you are going to operate.

: Never ASS U, ME as you make an ass of you and me.

: ASSUME NOTHING plumbing is a science and each system should be designed. This is not a one size fits all. You can design a system by figuring that only 75% of this system would be used at one and base your piping sizes to this factor.

: I hate a one pressure fits all mentality as folks running for examaple a hydronic heating line would certainly not want to have a velocity in excess of 3 FPS with any water temperature AT 180 degrees or higher.

: There are so many factors in plunbing and too many folks rather guess or use a very wide pressure range then doing the actual hoework required to being a "professional plumber"

: Your plumber sounds like he is right on the money

: Saying 40 -60 PSI is "average" sure leaves a lot to be desired when installing a piping system sight unseen.

: Is this a ranch or a multi story dwelling?

: Are there water meters that add a lot of friction loss. What size main. many one family homes I work in have an 11/2 Brass main YET I would never say 1"-2" is normal as some folks do have a fire suppression system (NFPA 13) taken off the water main

: What kind of materials are used for the piping.

: See it is not al that simple UNLESS your following
: the SPC/SBCCI then just about anything is ok as long as one really doesnt take health issues into consideration.

: Not all "codes" are good for civilized countries BUT pay offs have been known to have been made and inspectors can be bought so good luck.

:
:
Sylvan your right on the money, to many folks just connect to a water supply and keep on trucking along to the next tract house

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