Pressure Tanks in Series

[markinnc]

Grundfos has dry well protection built in... if that helps....
I dont think anything helps prevent short cycling when a tank fails..
Please correct me if I'm wrong here. But if your going to add a second tank, why not just replace the original one now (if your afraid of it)

Thank you - dry well protection does help as we worry about the well during periods of drought. Yes Cary taught me that there are control devices that read cycle time and cut off to prevent short cycling. A $250 device is more than 50% of the cost of a 44 gallon Water Worker.

The second tank solution seems a better approach because it adds draw down capacity (less pump cycles) and might save the need to buy all the additional plumbing equipment (valves, etc.) right now. Someone did allude to this not being the case above. I also am capable of doing basic PVC plumbing. If I do this, I am researching if the old tank can be left in place after it fails...

This is why I mentioned cost benefit analysis above. If I can buy a tank (+pvc) for security and then use the tank in the future build of the system, that seems very cost effective both now and into the future.

 

[markinnc]

You can buy a low pressure resettable pressure switch for about $40.

If the pressure drops too low it’ll cut your system off until you reset it.

​

I don't understand how short cycling relates to pressure. If I have a working pressure switch, how can pressure fall below say 40 when the tank fails? $40 is affordable insurance!!! Thank you!!!

 

[Twowaxhack]

​

I don't understand how short cycling relates to pressure. If I have a working pressure switch, how can pressure fall below say 40 when the tank fails? $40 is affordable insurance!!! Thank you!!!

I was responding to post #39, the first sentence specifically.

Here you can read this, it might help.
https://www.freshwatersystems.com/blogs/blog/well-pressure-tank-problems-and-how-to-fix-them

 

[markinnc]

I was responding to post #39.

39 is me and I confirmed that you are correct. I can put in a low pressure switch to protect the pump. When a tank fails the system does not properly hold pressure regardless of the pressure switch setting. Ignorance solved!!!!

Thank you - thank you - thank you! Days of effort for such a simple solution!!!!

 

[Twowaxhack]

39 is me and I confirmed that you are correct. I can put in a low pressure switch to protect the pump. When a tank fails the system does not properly hold pressure regardless of the pressure switch setting. Ignorance solved!!!!

Thank you - thank you - thank you! Days of effort for such a simple solution!!!!

Here’s post #39



I responded to his first sentence with this .

 

[Valveman]

Lots of good questions. As Mark noted I'm sure, I can talk on this subject for hours. It is hard for me to convey what I know about this subject in writing. But I will try. First, there is nothing a CSV can do to eliminate the damage to a pump and tank that has already occurred. But, the CSV can stop any further damage from cycling the minute it is installed. It is not uncommon for those older WX302 tanks to last 30-40 years, especially with systems that don't have much or any irrigation. You will probably get several more years of service without doing anything.

But, the first proactive thing I would do is add a CSV1A to the existing system. It will reduce the number of cycles per day making the pump and tank diaphragm last that much longer. Topping off the pressure tank at a rate of 1 GPM decreases the speed at which the diaphragm in the tank expands, cools the motor down before the pump is shut off, and eliminates the water hammer that would normally happen when the check valve slams shut from the wide open position. By just adding a Cycle Stop Valve you may not have to worry about the water system for the rest of your life.

Then if you must replace the pressure tank, the CSV will allow the use of a much smaller and less expensive tank. I would use only a 4.5 gallon size tank with the CSV, and certainly no larger than a 10 gallon size tank. The 10 gallon tank is what I use at my house with a 25 GPM, 2HP pump and a 50/70 pressure switch.

Now, how you would know that your tank is going bad is that the pump will cycle even faster than normal. Without a Cycle Stop Valve it should take about 2 minutes for a 10 GPM pump to put 20 gallons in an 86 gallon size tank. Setting the CSV1A at about 57 PSI while using a 40/60 switch it should take about 3 minutes to fill the tank. When the diaphragm in the tank goes bad or the tank loses air, it will take less and less time to fill the pressure tank. A fully waterlogged tank will cause the pump to cycle on and off just as fast as you can say click, click, click. If you do not want to take the chance of just noticing the tank is filling faster there are devices that look for a rapid cycle. Some look at different parameters. But the Cycle Sensor simply looks for the time it takes to fill the tank. When using a CSV and measuring that it takes 180 seconds to fill the 86 gallon size tank, the Rapid Cycle feature in the Cycle Sensor is set to like 160 seconds. When the tank loses some air charge and it only takes 159 seconds to fill the tank, the Cycle Sensor will shut the pump off and display RCYC for Rapid Cycle. Then you will know it is time to replace the tank long before the rapid cycling destroys the pump.

If you are worried that the well will pump dry, the secondary function of the Cycle Sensor is to save the pump from running dry. The pump will draw about 40% of full load amperage when pumping air. The Cycle Sensor Current Adjust feature is set like 50% of load and will shut the pump off when the well is dry. Many of the other brands of these devices do basically the same thing. If you do not have a Cycle Stop Valve on the pump any brand will work. Most look for +- 25% drop in amps and shut off the pump. If you have a Pentair or other pump that doesn't drop much in amps, those other brands of dry run protectors will even work with a Cycle Stop Valve. But if you have a pump with a floating stack design, the Cycle Stop Valve can make the amps drop as much as 60%. The Cycle Sensor is the only dry run protector I know if that has an adjustable underload feature. If the CSV makes the pump drop 60% amps the Cycle Sensor can be set to shut the pump off at 62% of load. So, the Cycle Sensor knows the slight difference in the low amps created when a Cycle Stop Valve restricts the pump down to 1 GPM flow and the slightly lower amps that happen when the pump runs dry.

A low pressure cut off pressure switch cannot protect a pump from rapid cycle. With a 40/60 switch the low pressure feature only shuts the pump off if the pressure gets below 30 PSI. Even with a waterlogged tank and the pump cycling on and off rapidly, it is still maintaining pressure between 40 and 60. Only when the rapid cycling causes the overload in the motor to trip will the pump fail to come back on at 40 PSI, letting the pressure drop below 30 and the little lever on the switch to fall. By that time there has been a tremendous amount of damage done to the pump. A low pressure cut off switch will also not shut the pump off when the pump runs dry UNLESS there is a faucet open at the time. A Cycle Sensor is a much more dependable and less problematic way to protect a pump from dry run or rapid cycle.


Lastly, the Grundfos SQ pump does have dry run protection built in. It is not adjustable and I think it just restarts the pump every 10 minutes and tries again. But the SQ pump does work well with a Cycle Stop Valve as well as a Cycle Sensor when more adjustability is needed.

 

[FishScreener]

Lots of good questions. As Mark noted I'm sure, I can talk on this subject for hours. It is hard for me to convey what I know about this subject in writing. But I will try. First, there is nothing a CSV can do to eliminate the damage to a pump and tank that has already occurred. But, the CSV can stop any further damage from cycling the minute it is installed. It is not uncommon for those older WX302 tanks to last 30-40 years, especially with systems that don't have much or any irrigation. You will probably get several more years of service without doing anything.

But, the first proactive thing I would do is add a CSV1A to the existing system. It will reduce the number of cycles per day making the pump and tank diaphragm last that much longer. Topping off the pressure tank at a rate of 1 GPM decreases the speed at which the diaphragm in the tank expands, cools the motor down before the pump is shut off, and eliminates the water hammer that would normally happen when the check valve slams shut from the wide open position. By just adding a Cycle Stop Valve you may not have to worry about the water system for the rest of your life.

Then if you must replace the pressure tank, the CSV will allow the use of a much smaller and less expensive tank. I would use only a 4.5 gallon size tank with the CSV, and certainly no larger than a 10 gallon size tank. The 10 gallon tank is what I use at my house with a 25 GPM, 2HP pump and a 50/70 pressure switch.

Now, how you would know that your tank is going bad is that the pump will cycle even faster than normal. Without a Cycle Stop Valve it should take about 2 minutes for a 10 GPM pump to put 20 gallons in an 86 gallon size tank. Setting the CSV1A at about 57 PSI while using a 40/60 switch it should take about 3 minutes to fill the tank. When the diaphragm in the tank goes bad or the tank loses air, it will take less and less time to fill the pressure tank. A fully waterlogged tank will cause the pump to cycle on and off just as fast as you can say click, click, click. If you do not want to take the chance of just noticing the tank is filling faster there are devices that look for a rapid cycle. Some look at different parameters. But the Cycle Sensor simply looks for the time it takes to fill the tank. When using a CSV and measuring that it takes 180 seconds to fill the 86 gallon size tank, the Rapid Cycle feature in the Cycle Sensor is set to like 160 seconds. When the tank loses some air charge and it only takes 159 seconds to fill the tank, the Cycle Sensor will shut the pump off and display RCYC for Rapid Cycle. Then you will know it is time to replace the tank long before the rapid cycling destroys the pump.

If you are worried that the well will pump dry, the secondary function of the Cycle Sensor is to save the pump from running dry. The pump will draw about 40% of full load amperage when pumping air. The Cycle Sensor Current Adjust feature is set like 50% of load and will shut the pump off when the well is dry. Many of the other brands of these devices do basically the same thing. If you do not have a Cycle Stop Valve on the pump any brand will work. Most look for +- 25% drop in amps and shut off the pump. If you have a Pentair or other pump that doesn't drop much in amps, those other brands of dry run protectors will even work with a Cycle Stop Valve. But if you have a pump with a floating stack design, the Cycle Stop Valve can make the amps drop as much as 60%. The Cycle Sensor is the only dry run protector I know if that has an adjustable underload feature. If the CSV makes the pump drop 60% amps the Cycle Sensor can be set to shut the pump off at 62% of load. So, the Cycle Sensor knows the slight difference in the low amps created when a Cycle Stop Valve restricts the pump down to 1 GPM flow and the slightly lower amps that happen when the pump runs dry.

A low pressure cut off pressure switch cannot protect a pump from rapid cycle. With a 40/60 switch the low pressure feature only shuts the pump off if the pressure gets below 30 PSI. Even with a waterlogged tank and the pump cycling on and off rapidly, it is still maintaining pressure between 40 and 60. Only when the rapid cycling causes the overload in the motor to trip will the pump fail to come back on at 40 PSI, letting the pressure drop below 30 and the little lever on the switch to fall. By that time there has been a tremendous amount of damage done to the pump. A low pressure cut off switch will also not shut the pump off when the pump runs dry UNLESS there is a faucet open at the time. A Cycle Sensor is a much more dependable and less problematic way to protect a pump from dry run or rapid cycle.


Lastly, the Grundfos SQ pump does have dry run protection built in. It is not adjustable and I think it just restarts the pump every 10 minutes and tries again. But the SQ pump does work well with a Cycle Stop Valve as well as a Cycle Sensor when more adjustability is needed.

General Comment on Pump Failures. The number one reason I have observed to cause a pump failure, it the pressure tank bladder has failed. Which fill the air chamber with water and causes severe short cycling. A pressure tank is generally sized to run the pump four or five minutes, long enough to cool the windings from the start. If you lose half the air volume, the pump short cycles.

I highly recommend that you valve off the pressure tank and then break the union, so it drains. Then try to pump the air chamber to 2-psi below the cut in pressure on the pressure switch. If the tank won't hold air pressure it has failed and needs to be replaced to prevent short cycling and destroying your new pump. Locally, they won't give you a warranty on the new pump, without verifying the existing pressure tank is airtight, or installing a new tank.

 

[Valveman]

General Comment on Pump Failures. The number one reason I have observed to cause a pump failure, it the pressure tank bladder has failed. Which fill the air chamber with water and causes severe short cycling. A pressure tank is generally sized to run the pump four or five minutes, long enough to cool the windings from the start. If you lose half the air volume, the pump short cycles.

I highly recommend that you valve off the pressure tank and then break the union, so it drains. Then try to pump the air chamber to 2-psi below the cut in pressure on the pressure switch. If the tank won't hold air pressure it has failed and needs to be replaced to prevent short cycling and destroying your new pump. Locally, they won't give you a warranty on the new pump, without verifying the existing pressure tank is airtight, or installing a new tank.

I can find tank sizing calculators on the web here. SELECTION TOOLS - Amtrol
They use 1 minute 1.5 minutes, and 2 minutes as the "target minimum run-cycle time".

A pressure tank sized to make the pump run for one minute is the standard. Two minutes of run time is considered a luxury. Sizing a tank any larger is rare. Most tanks are undersized because of cost. If tank manufacturers really suggested sizing a tank for four or five minutes of run time, the motor WOULD run long enough to dissipate the heat, and stay off long enough to cool down before restarting. It would also put so few cycles on the tank diaphragm that it would also last much longer. That is exactly why they do not recommend longer run times or continuous running, as that would make everything last longer.

That one minute of run time is designed for planned obsolescence as it causes exactly the scenario you describe. The pump cycles every minute and the tank diaphragm goes up and down every minute until the rubber tears and lets the air out. Then the tank gradually waterlogs causing the pump cycles to get shorter and shorter. If you do not have a device that looks for short cycles and you do not notice the lights flickering as the pump goes click, click, click a few thousand times for a week or so, you will need a new pump. This is even PLANNED to happen in an average of seven years, believe it or not. A new pump and a new tank every seven years for every pump system on the planet is the goal. I have even checked the date codes on thousands of pumps sent to the scrapyard over the years, and the average life expectancy overall is almost exactly seven years. Many will last 30-40 even 50 years. But average that with the ones that only last 3 or 30 days and the average comes out to seven years. For every pump that last 30 years, there is another that didn't last 15 days, which makes the average 7 years. Those are the two extreme of the dates, but the average works out the same with all pumps. If there is one thing pump and tank manufacturers are good at it is planning a failure date for their products. Pretty much anything that decreases pump cycling will increase pump life.

Many years ago I was ask to join a manufacturers group. After a little wining and dining the meetings were all about how to increase pump and tank sales. Marketing to new customers was one avenue. But conspiring and consolidating to plan the actual life of the equipment they made, blew my mind. Stupid and naïve, I could not believe they were making products with a limited life expectancy on purpose. Needless to say, I was out the door the next morning.

I went to many a pump school at the manufacturing plants where I was told this brand of pump is superior and last longer than the other brands because of blah, blah, blah. Then the other brand would tell me they were superior and lasted longer because of some great new sand slinger or other idea of some kind. Back home, I was out a lot of money fixing warranty pumps and still had angry customers. I could install the best pumps I could get in the best way I had been taught and they still averaged only seven years. My lucky customers who got 10-30 years were happy with me. But the ones that had warranty issues or just past warranty issues were angry at me, and I usually lost that customer to another installer, who was going through the same problems as me.

I know it is hard for people to believe that manufacturers would conspire against them. I felt the same way. But after being in the manufacturing side for many years now, I see that nearly everything is built with planned obsolescence as the major design criteria. It is a very hush hush secret, and I watch my back all the time because I know they don't like me to tell people about this. Over the years those same manufacturers have done everything they can to try and make me look foolish and condemn the Cycle Stop Valve for any reason they think of. Mostly, they just put ideas into people's heads at trade shows and hot dog days, and let installers and the general public post inaccurate comments or outlandish home made videos to make it seem there are problems with using a Cycle Stop Valve.

In reality, there are no problems for using a Cycle Stop Valve, just the opposite is true. As I have quoted a CEO at one of the major pump manufacturers many times, "The Cycle Stop Valve makes pumps last longer and use smaller pressure tanks, this company makes pumps and tanks, so anyone who mentions a Cycle Stop Valve will be terminated immediately".

 

[markinnc]

Merry Christmas to Cary and this board. I want to follow up and thank everyone for their patience and generosity in helping me to address my well concerns. Would you believe our clothes dryer failed yesterday?

I finally drained the pressure tank this morning. I got a reading of just under 21 pounds of pressure. I put in 7 pounds of air (28) reset the switch 3.5 turns to reduce the pressure to 30/50 from 40/60. Turned everything on and it cycled properly for 1.5 minutes. Darn near had a panic attack when kitchen faucet water pressure fell off in a few seconds. If I waited a minute and turned a faucet back on this condition repeated. I undid my 3.5 turns which set the switch to cycle between 35 and 55 (strange). This didn't correct the pressure fall off problem. Turned the shut off valve on and off a few times. Turned on an outside hose faucet and a bunch of sediment was ejected with the stream of water. Pressure is now fine. I imagine 28 lbs in the pressure tank vs the recommended 33 isn't a big deal? It is annoying that my well contractor didn't check the pressure tank.

P.S. I think it could benefit a future homeowner if I share what Cary said on the phone. Pressure tanks become water logged over time as the air chamber fills up. As the tank becomes water logged, pump cycle time is reduced. I can monitor for this situation to postpone additional expenditures without worrying that my new pump is in immediate danger.

 

[FishScreener]

Merry Christmas to Cary and this board. I want to follow up and thank everyone for their patience and generosity in helping me to address my well concerns. Would you believe our clothes dryer failed yesterday?

I finally drained the pressure tank this morning. I got a reading of just under 21 pounds of pressure. I put in 7 pounds of air (28) reset the switch 3.5 turns to reduce the pressure to 30/50 from 40/60. Turned everything on and it cycled properly for 1.5 minutes. Darn near had a panic attack when kitchen faucet water pressure fell off in a few seconds. If I waited a minute and turned a faucet back on this condition repeated. I undid my 3.5 turns which set the switch to cycle between 35 and 55 (strange). This didn't correct the pressure fall off problem. Turned the shut off valve on and off a few times. Turned on an outside hose faucet and a bunch of sediment was ejected with the stream of water. Pressure is now fine. I imagine 28 lbs in the pressure tank vs the recommended 33 isn't a big deal? It is annoying that my well contractor didn't check the pressure tank.

P.S. I think it could benefit a future homeowner if I share what Cary said on the phone. Pressure tanks become waterlogged over time as the air chamber fills up. As the tank becomes waterlogged, pump cycle time is reduced. I can monitor for this situation to postpone additional expenditures without worrying that my new pump is in immediate danger.

Most tanks sold today are the diaphragm type and have a rubber diaphragm which isolates the air chamber from water. And the air in the upper chamber above the diaphragm is preset to 2-psi less than the pump cut in pressure. Typically, there is no water movement into the air chamber unless the diaphragm is/has failed. Once a year, typically the best time is in the fall, when you quit irrigating. Drain the water out of the tank and verify the precharge pressure. I think Watts makes a fitting for installing pressure tanks, which has a port to drain the tank, without draining the whole system. The other option is to install a ball valve, and a union going to the tank, from the tee. You close the ball valve and then break the union open, and the tank will depressurize the water side, and let you check the precharge on the air side. If the pressure doesn't hold, the diaphragm has failed, and the tank needs to be replaced.

Most of the systems I designed were for Forest Service compounds. Which consisted of a few houses, a bunkhouse, and a small office. Because they were remote, we designed the water system to provide fire flow to, two 2-inch hoses while maintaining 40-PSI. So, we ended up with 3-hp pumps, and I designed for a 4-minute run time for the pump, just to make the pump last longer.

 

[Valveman]

Most tanks sold today are the diaphragm type and have a rubber diaphragm which isolates the air chamber from water. And the air in the upper chamber above the diaphragm is preset to 2-psi less than the pump cut in pressure. Typically, there is no water movement into the air chamber unless the diaphragm is/has failed. Once a year, typically the best time is in the fall, when you quit irrigating. Drain the water out of the tank and verify the precharge pressure. I think Watts makes a fitting for installing pressure tanks, which has a port to drain the tank, without draining the whole system. The other option is to install a ball valve, and a union going to the tank, from the tee. You close the ball valve and then break the union open, and the tank will depressurize the water side, and let you check the precharge on the air side. If the pressure doesn't hold, the diaphragm has failed, and the tank needs to be replaced.

Most of the systems I designed were for Forest Service compounds. Which consisted of a few houses, a bunkhouse, and a small office. Because they were remote, we designed the water system to provide fire flow to, two 2-inch hoses while maintaining 40-PSI. So, we ended up with 3-hp pumps, and I designed for a 4-minute run time for the pump, just to make the pump last longer.

That is a good way to check a tank. However, really any faucet will drain the tank. An 80 gallon pressure tank only holds 20 gallons of water. Draining the system requires turning off power to the pump and opening any faucet. When the 20 gallons from the tank is gone there really isn't much left in the system to drain. With any faucet open, if the tank will not hold 35-38 PSI of air, the diaphragm in the tank is bad.

50 GPM or so is common even in some houses for fire protection. With large horsepower pumps the 4 minute run time is a good idea. But that would take 10 of the 86 gallons size tanks ganged together to hold the 200 gallons needed. By using a larger Cycle Stop Valve with the 5 GPM minimum as needed to keep larger horsepower motors cool, a single 86 gallon size tank could give the same 4 minutes of run time. It would also eliminate cycling no matter the flow rate being used from 5 to 50 GPM, and give a mechanical soft start/stop, which is even more important on large systems.