installing a pressure tank

[CowboyUp]

I know this is a dumb question, but I'm a little slow and I can use some help with setting up my pressure tank. Will someone please explain to me how the pressure switch works? I know that the low number tells the pump when to come on, and I know that the high number tells the pump when to shut off, but what does the low number really mean? Does my well pump have to be pushing water at 20 or 30 psi before the pump will even come on? I'm greatly confused about the difference in a 20/40 switch and a 30/50 switch. Obviously, I want my water coming to my fixtures at the highest pressure, but how does that correlate with the low pressure number? If someone can please explain this to me, I'll be able to decide which pressure switch I need to buy and then I can hook my water up. By the way, I'm using a 24 volt dc pump. I have no idea how much pressure is being delivered at the well head. It seems to be a good steady flow, but I haven't put a gauge on it. Do I need to do that to choose my switch? Sorry if this is a dumb question, but I hope someone will explain it in simple terms so I can understand. Thanks for the responses.

[Bird]

If I understand your question, the pressures being measured are the pressures in the pressure tank itself, not the pressure provided by the pump. When the pressure inside the tank drops to the low number, the pump will come on, pump water into the tank until the pressure reaches the high number and will shut off. So the pressure at the faucets should always be somewhere between the low number and the high number.

[CowboyUp]

Thanks, Bird. That makes sense. I sure don't know why the plumbing expert at the big store wouldn't tell me that. I asked him what the low number meant. He said I needed to know how much pressure my well pump was delivering. I got confused!

[egon]

Perhaps the fellow giving advice in the store was confused !!

Downhole pump - shallow well pump - jet pump all have check valves at the bottom of the string.

Egon

[jimbrown]

If you are using a 24 volt pump I would stay with a 20/40 switch.
That 24 voult pump is ging to pull a lot of amps if it is pushing 50 or more lbs of pressure. This is going to be inportant if you are driving it with batteries. I have two 12 volt ones on mine and they pull 7 amps each at 40 lbs. Is this a boster pump or the actual well pump? I have a 60 volt submersible pump in my well that runs off of solar panels and the two booster pumps are seperate running off of panels and batteries.

[CowboyUp]

Jim,
I'm using the shurflo 9300 dc pump. I think you're right about the amps, but I'm hooking it up to my solar array and should have ample energy to allow the pump to operate even at higher amperage. Running it at 24 volts is a plus. How much difference would I see in water pressure between 40 psi and 50 psi? If the diff is nominal then I'll go with the 40. Another advantage of the 40 is that I'll have more drawdown water from my tank. Thanks for the input.

[jimbrown]

Ok I see what you are doing. You are going right from the well pump to the pressure tank. Most solar systems do not do this as it easy to run out of water at night or low sun conditions. Actually the draw down should be about the same. I have mine set at about 30on 40 off. That way the pressure pumps start running sooner. I find 40 lb plenty for my house and I run washer and dishwasher. Mine rarely drops to less thatn 20 lbs with both pumps running as that is about 5 gallons a minute. My down hole pump is a Dankoff and the pressure pumps are shurflow premium's. I am not sure how much pressure a 9300 will make but the higher the pressure the shorter the life span of the diaphrams in the pump. The well head pressure will depend more on your static water level than anything else plus what you have the pressure tank set for. My well pump is at 180 ft and flows about 2.5 gallons a minute into a 600 gallon tank. I am in the process of adding another 1200 gallon tank as I have come up short a couple times this winter when I had house guest who did not understand that it took sunlight to pump water. I have 4 60watt panels on the well and five 40 watt panels on the boost pumps with two golf cart batteries for night time.

[Pat]

Our Property in Baja Mexico is a solar only development. We have no wells and depend on water trucks delivering to tanks (underground, surface, or elevated) or haul your own in drums from water plant in nearest town (several reverse osmosis water vendors) I have little experience with pumping from wells with solar (just what I have read about 3rd world projects) but a lot of experience with pumping from tanks. Given your low gal/min capacity from the well, I'd think there may be instances where you might not meet your peak demand. A storage tank (I prefer in-ground) can be filled at whatever trickle your well pump will produce and then you use out of the tank.

As you are no doubt aware, you put a lot more amp-hours into a storage battery than you get out. In a situation like yours I would probably try to pump the well with straight solar (no batt) as much of the time as possible and store the water in the tank. Not a pressure tank, a storage tank. Then your battery-solar pump can pump from storage to the pressure tank on an as needed basis controlled by pressure switch. I think 40PSI is fine, unless you need LBJ showers.

This a a more energy efficient arrangement that gives you more performance from your panels and wastes less energy in the batteries. It requires that you have either a tank that is big enough to tide you over when there isn't enough solar power to pump the well or a backup switching system to temporarily run the well on batteries to avoid running out of water in extreme situations. It will likely require longer run times on the well pump at reduced flow rates to stay within your electrical production capabilities. So long as your average well production meets your average needs (as facilitated by the storage tank) you don't need to go to battery backup on the well.

One downside of the storage tank solution is the need for treating the stored water (chlorine...bleach.. or...) and then the need (I hate chlorinated water taste!!!) to remove the chlorine at point of use (activated charcoal filter and or RO unit.)

One small correction to other advice... the "STATIC" pressure in the house plumbing wil be the same as at the pressure tank IF AND ONLY IF NO WATER IS RUNNING ANYWHERE IN THE SYSTEM

Otherwise the pressure at any point of use will be something less than the tank pressure depending on pipe size and condition, flow rates, bends/elbows in the pipes, height of the point of use (you loose about 1 PSI per 2 foot of increased height at the point of use.) Probably not too important unless you have a 2 story or more building or pressures are marginal to start with.

[img]/forums/images/icons/smile.gif[/img] Pat [img]/forums/images/icons/smile.gif[/img]

[CowboyUp]

Thanks, Jim. I considered using a storage tank and a booster pump. But I opted to go straight to the pressure tank mainly because I don't expect to be using that many gallons of water per day. Of course, guest to the house will increase that usage, but I'll have to remind them to be frugal with water usage for now. I may add storage later, I'm just not sure. I'll see how things work without it. One issue that I was concerned about with the storage tank was exactly what Pat talks about. If I'm not running water out of that tank consistently, how am I going to keep that water fresh? And how much treatment will that stored water need?

[CowboyUp]

Thanks for the insight, Pat. I can easily pump from the well without the battery bank, but in order to do so, I'll have to add a solar panel designated solely for the well pump. At some point I may do so, but right now, I'll probably work on a minimal level- water production, water consumption- to save costs. In order to pump to a storage tank, I'll have to add a booster pump on the other end to pump to the pressure tank. Again, for now, I'll skip that, but later, as funds become available, I'll probably add on to the system. No doubt a storage tank will give me an ample water supply, and with my set up, it makes the most sense, but the pocket book tells me to get by with what I have for now, and add later. That's one good thing about my solar set up. I can easily add to it without having to scrap what I've already done. I lose nothing in the process of upgrading, I only gain. I made sure to overbuy on the inverter and charge controller so that as I added I didn't lose any of my initial investment. Going solar isn't cheap, but there are other benefits besides monetary ones, in my opinion. Thanks again.