I guess it doesn’t really matters if the bladder is good since the tank leaks through. You need another tank. I am guessing it really is a 10 GPM, 3 HP because of the 530’ depth. As Wellman said, that really means it will pump 12 GPM if the water is deep, and 16 GPM if it is not very far down to water. I am also guessing since you have a pumptec, that it is a low producing well. That means the well probably won’t produce 10 to 16 GPM. But since the well is so deep, you have a lot of water stored in it, so you can pump 10 to 16 GPM for a short time. I am also guessing that with 3 sprinkler heads on hoses, you are actually using about 6 to 9 GPM. With that size tank I will bet you hear the pump click on or off every couple of minutes. That is cycling which is not good.
Your options;
#1 Replace the tank with a similar size new tank (500 bucks?). Now to prevent the cycling, you should always run from 12 to 16 GPM all the time. Just means running about 6 hoses with sprinklers at the same time and getting finished sooner. The problem will be if your well makes less than 12 GPM, the well will pump dry when trying to use enough water to prevent the cycling. Hopefully the pumptec will shut it down before it burns up the pump (cost for a new pump?). If you don’t use enough water to prevent that clicking sound every couple of minutes, (cycling) will destroy your pump (cost for a new pump?).
#2 Since the well is only used for irrigation, you really don’t need a pressure tank (no cost). Just run it straight from the well to the hoses and sprinklers, and put a timer on the electric to the pump (maybe 50 bucks). Turn the pump on when you want water and off when you don’t, not the hoses. The problem will be high pressure. If you don’t run enough sprinklers for 12 to 16 GPM, the pump will produce enough pressure to blow up your hoses. You can’t use a pressure relief valve on this, so if somebody closes the hoses without turning the pump off (cost for a new pump???) If you run enough sprinklers to keep the pressure down, you may pump the well dry, same problem as with option #1 (cost for a new pump?)
Here you can use a Cycle Stop Valve (CSV1Z cost 200 bucks). The CSV will hold the sprinklers at a steady 50 PSI no matter how few sprinklers you run at one time. A small 75 PSI pressure relief valve (15 bucks) after the CSV will save your pump if someone accidentally closes off the hoses. With this set up I just wouldn’t run less than about 3 sprinklers at a time or the pressure before the CSV will get pretty high. I also would not put any valves on the hoses that could accidentally be shut off.
#3 Use two Cycle Stop Valves (CSV1Z) and a small 4.4 gallon size tank.(cost 500 bucks) You really only need the second CSV if your static water level is less than 300’. I am just assuming it is, so I am saying two CSV’s. A static of less than 300’ means you will have pretty high pressure before the CSV. So we use two CSV’s to stair step the pressure down from say 300 to 50 PSI. Doing this with just one CSV would work, it would just cut the guts out of the CSV eventually. With two CSV’s it will last a long time. With this set up you can continue to use the hoses and timers the same as you always have, and use as little as 2 GPM without hurting anything.
#4 Convert to a VFD, or variable speed pump. You most likely have a single phase motor, so you would need to pull the pump and replace it with a new three phase motor. (Cost of a new motor???) Then you need to purchase a VFD and pressure sensor (guessing 1,000 bucks) And you will still need at least a 4.5 gallon size tank. (100 bucks) With this set up you can sort of continue to use the hoses and timers the same as you always have. The only difference being that you always need to use at least 7 GPM, or there is not enough flow to keep a VFD controlled motor cool. (cost??) Hopefully your well will make at least 7 GPM to make this work. You will still have problems if you try to run more sprinklers than the well can keep up with. Hopefully the VFD will shut it down if you pump the well dry, if not (cost???) Long wires from VFD to motor (530’) causes reflective waves, which just means it is always sending high voltage spikes to the motor. (cost for a mew motor and/or wire?) Varying the speed with a VFD causes vibration from resonance frequencies, which just means every component in the pump and motor vibrates when not at full speed. (cost for a new pump and motor??) Harmonics are introduced by the VFD, which just means the motor runs hotter and every electrical device in the neighborhood is running on trashy voltage, making everything less efficient. (cost???) VFD’s and the motors they control don’t usually last very long, even when the VFD is installed in a dust free, air conditioned room. (cost to replace motor and VFD maybe every 3 years???)
I hear from at least one pump installer everyday who is just figuring this out. It usually takes them from 3 to 5 years of installing VFD’s. One I talked to today was from Canada. He said he spent 1 month out of 12 last year doing warranty work on VFD pumps. The pump company even wrote him a big check for his labor. He must be a good customer because they usually don’t pay labor. Even with part of his labor paid, he is still losing money and ruining his reputation. Even if half of all VFD’s are replaced under warranty, the pump company will make it back on the ones that fail just past the warranty period. The warranty period doesn’t start over with the “free” replacement pump. So you have to purchase the next one to get a new warranty. Even if they have a five year warranty, it pretty much means you are going to shell out for a new one at least every five years. With VFD’s, the pump man and the end users are the ones who lose out, and the manufacturer is laughing all the way to the bank.
Sometimes it takes a complicated explanation to make an easy decision.
