pressure tank advice

[audrey]

New member here...love the site!

Our pressure tank has rusted and leaked through.

Well-x-trol WX252
3hp 10gpm 530 ft (installed 2000)
40/60 pressure switch
pumptec plus

The previous owners used this set up to supply a 3bed/3bath house and 1 acre of landscaped yard. When we bought the house in 2006 the house had converted to city water so now just the yard uses the well. The yard is sprinkled mainly above ground using 4 main hose bibs with timers that are then split to 2 or 3 garden hoses with sprinkler heads. After reading some posts we realize that the bladder was probably burst for some time and hence the tank rusted through. Are we right in thinking the size of equipment is too large for our needs now?

Need advice on whether a small pressure tank and a cycle stop valve would be the way to go. Also, would we then be able to reduced the size of the pump when it fails in the future. Is it more economical to set our timers to run as many sprinklers as possible at once rather than them taking turns.

All advice is appreciated and thanks in advance.

Audrey

[Texas Wellman]

Have you emptied the tank and tested the bladder? If water comes out of the air valve then it's probably bad. If no water comes out and the tank will completely empty it just might need air. I would at least try to see if this tank holds air.

The main factor on the equipment size is can you keep it running without cycling very much. I know you said it's a 10 GPM pump but what does the pump really pump? That will depend on the pumping level and outlet pressure. If by keeping all zones going you can keep the pump from cycling then you are OK. If the pump "beats" the sprinklers I would either consider a cycle reducing valve or a VFD system, depending upon your needs.

Good luck.

[justwater]

small tanks and CSV's work great for irrigation. imo irrigation is where the csv truly shines. then whenever the pump fails u can determine if u want more volume or more run time.

[valveman]

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.

[audrey]

Thank you all for your input and detailed advice. We have a few options and we will need to consider them all carefully. I'll be back with more questions soon.

Thanks,
Audrey

[Texas Wellman]

Valveman gave you very good advice.

I would like to make one correction to his advice. There is a VFD made for single phase motors. The only drawback is that it can only lower the operating speed, not increase it like a 3-phase motor. I do not know if it can be used on a higher horsepower pump such as yours so it may be a moot point.

Valveman does not like VFD's and he sells the competitor to VFD's but they are a tool and they do have a place. However, I would probably go with either option 2 or 3.

Valveman why can't you use a pressure relief valve on option #2? One thing to remember is that sprinklers can get plugged even if there are no shutoff valves in the system so beware that you could still deadhead the pump or at least run it at higher pressures than expected.

[valveman]

I don’t think I made a mistake. I believe the Monodrive XT for single phase motors only works up to 2 HP. Which is good, so your not tempted to try it. The VFD’s that use a three phase motor and speed up the pump from 3450 to 4700 RPM, only serve to wear the pump out that much quicker.

I don’t hate VFD’s because I sell a competing product. I designed a competing product BECAUSE I hate VFD’s. I had several years experience with VFD’s before 1992. Back then we were smart enough to ALWAYS use valves for a VFD bypass. That way WHEN the VFD failed, we were able to switch over to valve control to dependable supply water to the customer. So every system I installed could be easily switched from VFD to valve control with the flick of a switch. With these systems we were comparing VFD’s to valve control everyday on every system.

With these dual control systems, it was very easy to see all the VFD problems I talk about with resonance vibration, harmonics, voltage spikes, bearing currents, lack of dependability, and other things. It was always an eye opener to flick the switch to valve control and see all these problems disappear instantly. It was even more of an eye opener to switch from VFD to valve control, and see that the power consumption was the same.

I studied electronics in school and even built a computer from scratch in 1977, so I like electronic gadgets. I studied every VFD I could get my hands on in the 80’s, and even did my own programming and tried to fix some of the inherent problems with VFD controls. Unfortunately the problems with VFD’s are dictated by the laws of physics, so they can never be solved. Since the last VFD I installed in 1991, they have made many changes. VFD’s have gotten smaller, cheaper, faster, and easier to program, but these are just band-aids. When I realized the real problems with VFD’s can never be solved unless you can change the laws of physics, I switched to valves and never looked back.

It is intuitive to think slowing the RPM of a motor will decrease the energy used, and restricting a pump with a valve burns energy. However, the natural characteristic of centrifugal impellers is one of the few things in this world that is counter intuitive. Restricting with a valve decreases energy consumption as much as varying the speed. You really have to understand the natural characteristics of pumps to see this. The majority of people in the pump industry do not understand this, so the average person is really at a loss. The VFD industry capitalizes on this “myth-understanding”. They promote VFD’s as energy saving devices, and the vast majority of people fall for this hook, line, and sinker. In reality reducing the RPM with a VFD can cause as much as 500% more energy used per gallon produced, not to mention all the other problems I listed. It is kind of like being so sure that the earth is flat, that you refuse to get on the boat and see for yourself that this is wrong.

I think the VFD is a wonderful invention that has come a long way since it was introduced in 1968. The VFD certainly has lots of good application for escalators, elevators, conveyor belts, treadmills, even hybrid cars. We should just understand where they are useful and where they are not. And pump systems that must produce a certain amount of pressure, are one of those applications where the VFD is more trouble than it is worth. I am not bragging or criticizing others when I say that anyone who doesn’t understand these things is at least 20 years behind.

Technology that changes the way we do things is only obvious in hind-sight to most people. Manufacturers spend the most money marketing products that make manufacturers the most money. Tons and tons of money is being spent marketing VFD’s. So tons and tons of money is needlessly flying out of consumer’s pockets. Pump installers and consumers who drink the tainted Cool-Aid and fall for the VFD marketing ploy, will have to learn the hard way.

And I guess you can use a pressure relief valve on a manual system without a CSV. The pressure relief will just pop off anytime you don’t have enough hoses running.

[Texas Wellman]

Valveman I'm not really looking to get into an argument with you over VFD's vs. CSV's. I just wanted to bring up a few points.

I'm well aware of the laws of physics and exactly what happens with energy consumption etc. I have never stated that VFD's save energy, that's not really their purpose. But you fail to mention that the same laws of physics apply to a VFD on the slow part of the curve where they use more energy but when the pump speeds up they actually use less energy so depending upon the application it may be a wash on the energy use.

VFD's are a tool as are CSV's. They are not always the best choice for the situation which is why one must carefully weigh the pro's and con's. Motors run on a rotating magnetic field, the VFD's change the characteristics of that field. Yes, they are quite expensive and there can be problems but can be a good solution. No one size fits all.

Good luck.

[valveman]

I think we explained the best options. You brought up VFD’s, and I never mind a good argument. I have been “weighing the pro’s and con’s” of this subject for long time.

I read where you had been to the Franklin school. So I know what you have been told, and I wish you luck with that.

If you care to elaborate more on the VFD, or point out anything I have incorrect, it would be appreciated. I am a little confused about this statement.

“But you fail to mention that the same laws of physics apply to a VFD on the slow part of the curve where they use more energy but when the pump speeds up they actually use less energy so depending upon the application it may be a wash on the energy use.”

If you are frozen in like I am, maybe you could take the time to expand on this for me?

[Texas Wellman]

Cary,

Don't want to hijack this lady's thread. I do believe that VFD's are not appropriate for an average residential use application. I think a CSV is a nice product and more suitable for her application. I think the CSV is probably the best choice for her.