This is a question that you must direct to your local zoning commission.

The primary purpose of the Plumbing code is to insure a safe source of potable water and proper discharge of waste.

In order to insure that there can be no cross contamintation
the plumbing codes expressly prohibit connecting a home well or private water source to a system that is fed by a municipal or corporate water supply.

uhhhh.....no zone here, we be mountain folk, no contamination either, its all the same source, its just a supply reserve. The backup tank cant contaminate the neighborhood supply cause it would have to get past a one way valve + 300feet straight-up to the cisterns on top of the mountain and then back down again through someone else's access point.
Thanks anyway, I just want to know about pressure tank vs constant pump is all.

Pressure tank. Definitely. A demand pump will likely wear out quickly and be a real pain, particularly since home water use varies so much. Pumps prefer to provide a constant flow. Plus, with a pressure tank you still have water (for a while) during a power outage.

You could go either way with the pumps. If you choose to use a shallow well pump, then you will also need a pressure tank to store the water in and pressurize the system. That system takes up more room than going with a booster pump.

Check out the MQ-45 Grundfos booster pump. It's real easy to install. Just plugs into the outlet and takes up very little space. It would be my choice.

Both pumps have to run to make water pressure. The booster pump only runs when water is being used whereas the shallow well pump turns on whenever the pressure drops below a preset value, such as 30 psi and then it continues to run after the tap is closed because it has to refill the pressure tank and create pressure high enough to turn itself off. With the booster pump, you don't get the wide swings in pressure you do with the shallow well pressure system.

Thanks!
Yes, the Grundfos MQ-45 is exactly what I had in mind!
I asked them (worldwide power&pump) about noise and longevity. They said to just make sure it doesnt get too wet and put it indoors if possible. They also said its very quiet. My only concern is going to be regulating the pressure in when it is being fed by the neighborhood system instead of my back-up tank. I guess I can install a pressure reducer (if there is such a thing) just before the inlet to the pump.
The pressure tank can always be added later if the pump proves faulty I guess. the only complexity now is how to run it so the backup tank and the neighborhood supply can feed it easily. I can run everything off the tank but the neighbors will get PO'd if they do a trucked-in water supply this summer and my tank immediately sucks 2500gallons of community water before anyone else has a chance. I am still working out that part.
Thanks for the help everyone!

egor:
My wife used to live near Santa Ynez and had the exact same issue. She wanted a tank for fire protection backup, and her neighbors objected for the same reasons. She just dealt directly with the company that trucks up the water, and had them make a delivery just for her. That satisfied the neighbors.

Do you have attic or roof space for a tank? Even just a 100 gallon tank in the attic can supply sufficient pressure for most people in a 2-story home. You could use a small booster pump to get it from your main tank to the "daytank" in the attic or on the roof. Then you would have extra storage, and not need a pressure tank. I installed systems like this at my family's mountain cabins (no electricity, water coming from nearby spring using solar-powered pump). Works great.

The main purpose behind a booster pump, such as the MQ-45, is to provide decent water pressure inside homes when the municipal system is incapable of doing so. The MQ doesn't care about what the incoming line pressure is. In fact, it will pull water from your holding tank and give you excellent pressure throughout your home.

You never mentioned sort of pressure you are getting from the community system. If this was my home, I would install the Grundfos into the main line feeding my plumbing system but I would put a Tee plus two ball-valves to control the water coming from the sources. One ball-valve to shut off the holding tank while I was drawing water from the community line and one to shut off the community line while I was drawing from the holding tank.

Another option would be to feed the community line directly into the holding tank and install a valve on it that was controlled by a float. The community line would keep the tank full at all times and the Grundfos would give you the pressure for your system any time water was needed. Once the tank was full, you wouldn't be drawing an ounce more water than anyone else. The only difference between them and you would be your reserve tank capacity acting as a buffer whenever water becomes scarce.

As long as you are not blatantly using water to wash your car or supply an in-ground irrigation system for your lawn, no one should get upset.

Thanks for the excellent info, everyone! Much appreciated.
The reason I was concerned about the inlet pressure before the pump was because it was explained to me that the Grundfos pump amplifies incoming pressure, or adds 45psi to it. My 10ft tank will be about 4psi (if2.5ft=1psi), but the community system, when working well, is prolly already 40-50psi goin in, and I dont want, and I doubt my 75year old plumbing could handle 100psi. Am I wrong about this?
I like the idea of running off the tank with a float switch. The problem there is that once the community system stops filling the tank, a few days may go by before they have the emergency water trucked up. By then, my house of 4 people will have used about 250-400gals by my estimate. If we go longer, which sometimes happens,The tank would suck that from the community cisterns immediately upon filling, but your right, it isnt that bad. And nobody up here waters lawns or washes cars with our water! We'd all be marching to their house with pitchforks and torches,
yaknowwaddImean? :)
Matt: I like your idea of putting a spare 100gals or so up on the roof, would that provide enough pressure for a 2-story house with 2 bathrooms, 4people, and 50gal water heater? Also I would have to add a third line into the house and another to fill the spare on the roof. But definitely worth considering.

egor:
You get about 15 psi for every 32 feet of height, so unless you can get the tank well above the house you are not going to get the 40-60 psi that most people are happy with when running off a well. It is enough for cooking and washing dishes, filling toilet tanks (slowly), etc., but you won't have much more than a dribble coming out of your low-flow shower head. Our families' cabins are on steep terrain so I was able to put the tanks well above them, giving about 40 psi into the structures. In a standard house, they would be considered more of an emergency pressure source, such as during a power outage. However, the higher you can get your tank, the less amount of boost you need to get to the water pressure you want.

There are valves which municipalities require if you have a combined system, and that might be useful to you.

We have a well but are on city water. We are required to have, and to maintain and to have inspected annually, a backflow prevention valve. This happens to be a Watts 3/4" 0093M3 QT, and cost about $168.40, IRRC. We paid to have it installed and pay $50.00/annum for the inspection.

We use the well for irrigation and for the heatpump, but it is not connected to our house plumbing. The valve is required nonetheless, presumably because we certainly could hook the well to the house plumbing with little difficulty.

Good luck,

M

Thanks, M
But as stated before, you give far too much credit to my community calling it a "municipality" :)
Think 1800's mountain village + electricity and internet access. (we got that cause some hollywood bigshot wanted DSL and the phone company told him it would cost $100K to bring it up there and he said "OK, can you have it up here by Wednesday?" ) He's gone now but we all still have the dsl!!
Other than that, its just 12 houses with some oldtimers trying to keep anyone else from movin up here. They doin a good job, but I grew up in rural VA and dont scare easy. :)
I have put in a one-way valve to keep any of my precious water from feedin anyone else, though, but no annual inspection. The house was built turn o the century (19th) and was originally a stop for gold miners and people goin to LA

Why don't you just drill your own well? I read the part about the neighbors didn't want you too. Well if you own the land why could you not drill a well on your land?? If they have wells why can't you? Also if they have the wells why does everyone use a spring and then fight about trucking in water? Do all the wells go dry? I just didn't get the full picture I guess.

Hi Sparky823,
your questions are valid, I will try and explain, as best I can.
1. I can drill a well on my own land, but water law would then expose me to lawsuits from neighbors with shallow wells. They could claim I dried up their wells even if their wells have been dry for decades. They may even be waiting for me to do it so they can cash-in on the lawsuit. There is no way to prove either way, of course, but legal precedent in these matters is on their side. Besides, this is a small community and if I alienate someone, I am gonna have to live with them for a very long time and living in a neighborhood where people hate you is the pitts. Soon someone will buy one of their houses and maybe join us non-well-owners side and the balance of power will have shifted. But this is Santa Barbara, and even a piss-poor shack in the woods goes for $2million nowadays so it may be a while.
2.They have wells because their houses were built before mine long ago and my house was probably a guest house or something. There are about 6 houses with shallow wells and 6 without. These wells are shallow, dry or drying, and contaminated but allow the owners of those properties to not have to pay anything for the sketchy water system, even though everyone knows they use the same water from the spring as the rest of us. Those of us who do not have wells pay $25/house/month + $15/person/month for upkeep of the existing water system, such as it is. And who controls the sketchy water system? You guessed it, the shallow well owners! So they are making bank off it to boot. I cant do anything about it, water wars are the history of California and it wont change.
So when water is trucked in, they want 1st dibs on it even though us non-well owners are who is paying for it. Its not fair and I may, as I said, go to war over it; but I have only lived here for 7years and some of these bastards have been here for 70+years. I think I can just wait em out, but every year I get angrier. I may drill a deep water well (6-800 feet) if I could hide the operation in my basement or something, but I doubt that its feasible, and I obviously dont know how to drill wells.
So they claim they are living off their wells and dont want to lose their "freedom"; and for now I am trying to "get along". But I will not put up with this nonsense much longer and will appeal to the state health board or some government agency to override them if water still runs out.