Questions about Pressure Tanks

[Rayzen]

I live on the bank of a river, near the mountains, in Washington, and pump water out of it for the lawns, as well as for the veggie garden, during the hot, dry summers.

From the river, the water goes into an old pumphouse, where there is a pressure tank, then it continues out to the irrigation system. The pumphouse and pressure tank were part of an old well system for the house, which is no longer used, and the whole set-up is now completely separate from the house, so there is nothing else in the set-up.

The other day, I noticed that the pump was cycling on & off too often, and I figured that my pressure tank had become water-logged, so I turned the pump off, bled the tank, and measured the pressure. It was only 23 p.s.i. Using a bicycle pump, I tried to pump it back up to about 38 p.s.i., but now it won’t take any pressure at all. I guess it’s dead, which figures, since it’s probably over twenty years old. I certainly got my money’s worth out of it, so there’re no complaints in that department.

But now all of that raises new questions. If I’m going to restore everything to the way it was, I will have to go through a lot of expense and hassle. Since I don’t own a truck, I will have to not only pay for a new water tank, but also to have it delivered. In addition, I will have to dismantle my pumphouse, then go through the disassembly and reassembly of the new tank. All of that is certainly not a huge, impossible issue, but I’m wondering if it’s really necessary. My next-door neighbor also pumps water out of the river for his lawns, and he doesn’t use any kind of a pressure tank. He simply sticks a foot valve in the river, pumps the water up the hill and directly to his sprinkler heads. He has done this, now, for thirteen years, without any problems, whatsoever. He has the whole thing on a timer, and runs eight sprinkler heads, which come on for about 15 minutes, then shut off, again, each day. I called a plumber, the other day, and when I described my neighbor’s set-up, he said that not having a pressure tank was “ideal,†since the pump would come on, then just run continuously until it shut off again, without any switching on & off. That sounded a little crazy to me, but I didn’t want to insult him, so I didn’t say anything.

So, here are my questions:
• Is a pressure tank really necessary? Judging from my neighbor, it wouldn’t seem to be.
• If it’s not really necessary, then why are pressure tanks used, at all?
• Was the plumber who I talked to correct? Once again, if he is correct, then it makes me wonder why anyone would bother with a pressure tank, at all.

Here’s my guess on the whole thing: it would seem to me that a pressure tank, having an air bag in it, would act kinda like a shock absorber, allowing the water to push on the air over a greater time period, after the pump shuts off, than it would if there were no air bag in the system. This would then lessen the sudden shock to the pump, upon shut-off, making it less stressful on the pump. Am I right about that? Is that the real function of a water tank-air bag set-up, aside from storing a few gallons of water at a time? If so, then how is my neighbor getting away without having one?

Do I really need to get a pressure tank, or can I just do what my neighbor’s doing?

Any help/advice would really be appreciated, since I’m clueless as to how to proceed, here, and my lawns are beginning to show some stress from the current dry spell.

 

[Ballvalve]

You dont need the tank, and can leave the bad one in place if need be. You will need to adjust the pump to maintain the correct pressure on your irrigation - tweaking the pressure switch or restricting the outflow. Tanks are essential for varied uses, but not not in a fixed flow condition. Start by just turning it on and see if it maintains pressure and does not try and shut off during irrigation.

 

[Sponsor]

 

[Rayzen]

Thanks for that reply; it helped, as now I know that I can just skip the tank and leave the old one in place. That saves me a lot of time, money, and hassle.

Today, I disconnected the pressure switch, plugging the spot on the pump where the tubing attached. So now, when I switch the pump on, it runs continuously. I planned on going to the store, tomorrow, to buy an electric timer, and set it to come on about three times each day for about fifteen minutes, each time. Does that sound like a decent way to do it?

The reason I got into this was because my pump was cycling on & off every minutes or so, as the pressure dropped, while I was watering the lawns. The pump would click off at 60 p.s.i, then, as the sprinklers ran, it would drop down to about 40 p.s.i within just a minute or so, then click back on again. So the pump was coming on & off every minute, which I figured wasn't too good for it; seems like it should have a longer "rest" in between times of coming back on, so as to keep from overheating (at least five or ten minutes, right?). I know it's not the running that's so hard on the motor, but rather the frequent switching on that is the problem, as there is a lot of current which flows through a motor's windings, when it first starts and hasn't built up any counter e.m.f., while coming up to speed.

So, in order to keep the on-off cycling from occurring so often, I opted to just disconnect the pressure switch tube and go with an electrical timer, which would turn it on, as stated, only three times, each day (maybe once in the early morning, once in the middle of the day, and once in the late evening). In this way, it would then run continuously for about fifteen minutes, each time it switched on. Is that a logical way of going about it, in your opinion?

But, today, I ran into a problem, when I disconnected the pressure switch and tried the whole thing out, to see if it worked as planned. After priming it with a garden hose from the house supply, it started up fine and I had great pressure (about 50 p.s.i.) and water coming out of every sprinkler head, but after a few minutes, the pressure dropped down to about 22 p.s.i, and water was just barely coming out of the sprinkler heads. That is about the pressure which I get from the pump which is down on the river (seventeen feet below the pumphouse), so I'm suspecting that the pump in the pumphouse is losing its prime and the only one that pushing water into my sprinklers is the one down on the river. The one down on the river is a 1/2 h.p. pump, and the one in the pumphouse is a 1 1/4 h.p. pump. So, here are my five new questions: (sure glad you are patient with us non-plumbers)

-- Is there a way to find an air leak which would be causing a pump to lose its prime? Some nifty little tip/trick that can be use kinda like when you find a hole in an innertube, by sticking it in a tub of water? (By the way, when I plugged the hole where the pressure switch tube connected to the pump, I use a normal threaded plug and plumber's tape, so I'm really sure that it's not leaking air in at that point)
-- Could the problem somehow be the fact that I have a larger (1 1/4 h.p.) pump up in the pumphouse, which is in the line after the smaller pump (1/2 h.p.) down on the river?
--Can you just add the horsepower of each pump, to get a total, or is that not how it works? I need at least 1 h.p., in order to lift the river water the 17 feet up the bank and still have enough pressure (50 p.s.i) to run all of the sprinkler heads, giving me enough g.p.m. flow. If you can add’em, then I have 1 ¾ h.p., total.
--My next-door neighbor has a 1 1/4 h.p. pump running his eight sprinkler heads and he is the same distance above the river as I am, yet he gets way more pressure out of his than I do, even at first, when I have full pressure, before the pumphouse pump loses prime (if that's what's really going on; dunno, though). So, if I have more h.p. than him, why does he still have more pressure on his sprinkler heads than I do? Actually, he doesn't even know how much pressure he has in his irrigation system, as he doesn't have a pressure gauge in it, anywhere. But his sprinklers come on like Gang Busters, when they come on, and he gets water thrown way out, whereas mine fizzle down to about nothing, if I turn all of the sprinkler heads on. How can I have more h.p., and be lifting the water the same height, yet have less pressure than him?
--My neighbor has much larger plastic pipes running through his irrigation system than I do; would that account for the fact that he is able to get way more water than me, even though I have seemingly more h.p. than him? (if the pumps can be added together, like that)

Once again, thanks a lot for your time and helpful advice. I appreciate it!

 

[Ballvalve]

Small pipe and drawing water through a .5 hp pump with a 1.25hp pump is an abnormal situation ripe for weird problems. You can go on a suction leak hunt - very problematic- with pipe cement and dope and even caulk, but I would just move the big pump down to the river and use only it. If you dont get enough flow add in the other pump in parallel, tee'd t o the outlet of the big pump. [2 pipes into the river for pick up]

I do not think that will be needed, [2 pumps] and should be avoided.

You might have a restriction in the water pickup system in the river, that might cause some cavitation in the small pump and add air slowly into the system.

The pipe size for the inlet and outlet of the big pump should be exactly what is on the pump or larger. If its sized way down, you can forget matching the neighbors performance.

I would use 1 large pump as close to the pick up as possible. Make sure no restriction in the river pick-up, and run larger pipe - probably 1.25" up to the manifold to the sprinklers.

And by the way, you will not get a good timer that will do 15 minute increments at the true value store unless you are very lucky. Look for the Intermatic or Graslin GD40 [I think] its good for 40 amps and has a German made timer of top quality. About 60 bucks from a place called 1000 bulbs. Search this forum for a post I made about it a few weeks ago.

I would also bypass the old tank and eliminate any elbows and tees that are not absolutley needed.