Out here, I think they put the tanks up in the hills. Possibly there are pressurized reservoirs, but I doubt it.

Our irrigation system, which drops forty feet down hill, has a whopping 100 psi at the bottom of the hill. Our houshold psi is 70, which is too high, and I need to get the plumber back to fix the pressure regulator. But I do like the strong shower!

Looking up the exact figures, 1 atmosphere is 14.7 lbs/sq in, and 1 atm pressure is exerted by sea water at 32 ft below the surface. (It varies slightly in fresh water, due to the different density).

You always have to take into account normal atmospheric pressure at earth’s surace when dealing with these kinds of problems, so I assume when you say tap water comes out at 50 psi, I assume you mean 50 psi ABOVE atmospheric pressure. In other words, in airless space, your faucet would be operating at 64.7 psi. Likewise the pressure under 32 feet of sea water is actually 29.4 psi, taking into account the added weight of atmosphere above the ocean. Pressure is always meansured against some standard, and that standard is 1 atm on earth.

Since the weight of the atmosphere affects your faucet pressure in exactly the same way it affects the sea, we can ignore it, so the depth at which ocean pressure exactly balances your 50 psi faucet is 50/14.7 x 32 = 108.84 feet. Any deeper and the pressure will force water up into your faucet.

I’ve done 14,695 in 12 hours, from the top of Mt. Whitney at 9:00 AM to – 200′ ASL in Death Valley at 9:00 PM. From 8,300′ to Death Valley was in a car.

As it turns out, water pressure increases at a rate of roughly 1 atmosphere for every 30 feet or so of water depth. (It is already 15 lb/sq in at the surface due to the weight of earth’s atmosphere.) So if you dive to the bottom of a 30 foot pool by holding your breath, the water pressure outside is double the air pressure inside your lungs.

So for 2 atmospheres of water pressure coming out of your faucet, going down 30 feet will just counteract it. Any deeper and water will flow IN your faucet.

It helps doing this kind of problem to keep in mind that a column of water 1 inch square and 30 feet high weighs about 15 lbs.

And a column of air 1 inch square reaching all the way to the top of our atmosphere will also way weigh about 15 lbs.

“Pressure at this depth would force water back up a household faucet”

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