Which is why regulators are required inside. However, quite frequently
water pressure will drop dramatically as a result of mass usage. Especially in cold weather when water mains break.
The water pressure in my house is about 60PSI and when I use a “sprinkler hose” the water pressure is equal all along the line. Then the end of the hose comes off and the pressure within the hose drops at the “sprinklers” but not at the end where it shoots out.
This is not the case with electricity. Wires connected to a main feed produce a certain amount of current (through amperage) to each terminal. If the end of the wire is cut, the current maintains its “pressure”, or amperage, to each terminal–the electricity does not flow aimlessly out of the end of the wire as it does with a hose.
The water-electrical analogy is high-school physics used to visually demonstrate the concept of amperage as a “pressure”, so to speak. It really doesn’t go much further than that. It does make it easier to understand that which can’t be seen.
60 PSI is an average range for a public water supply if it is higher than that you should install a pressure reducing valve on the line. I have seen it over 90 psi
“Where the water pressure exceeds 80 or 100 psi (depending on your jurisdiction) pressure regulators may be required to limit the house supply pressure to 80 psi.”
Principles of Home Inspections
Systems & Standards
Dearborn Home Inspection
page 788
First sentence of the first paragraph of Excess Pressure within the section of Supply Piping Distribute System in the House.
No mention of any specific low rang pressure is ever mentioned in this book. 80 psi is the limit around here and thus my answer is 80 psi.
The city is required to supply at least 40 psi per national codes. The city really could care less if they supply over 80 psi water pressure to a house. The house builder should regulate the pressure to less than 80 psi.
Hence the way the question was worded to get the discussion going and get people thinking.
