Pump torque in tank

[dchurch]

I did some searching/reading but haven’t been able to find a solution.

I've been using a submersible pump plumbed vertical in a 1700 gal poly tank for almost 20 years. I have zero complaints about the water system except... A few years ago I upgraded from a 3/4 HP pump to 1 HP. Now we are getting cronic torque damage to the submerged PVC plumbing. This will be my 3rd repair in the past 3 years!

The tank is above ground being feed by gravity spring water used for irrigation. The 1 HP pump is suspended vertically by 1 1/4" sch 80 PVC and 2 rope lines tied to a stainless eye-bolt. The 1 1/4" exits the tank through the tank sidewall near its top rim.

I currently have about 4 feet of submerged PVC pipe above the pump with a check valve and a union, then the PVC elbow that exits the tank. The torque caused damage has always occurred between the pump and the union. The first failure was a section of the PVC pipe deformed and split. Last time a male fitting split at the treads. This time it looks like the damage is to where the pipe enters the union. I wouldn't mind having to do the repairs if they weren't so frequent.

I could use some ideas here.

Maybe black poly pipe could handle the torque better than the more rigid schedule 80?
I'm not sure how well the slip fitting would hold up.

I am aware of torque arrestors but don’t see the application with this setup because my pump cooling sleeve is not connected to anything...

I've consider using metal pipe near the pump but fear the torque will simply cause problems further up the line.

 

[Valveman]

Torque only happens when the pump cycles on. Using a Cycle Stop Valve to decrease the cycles by say 75% will also decrease the problems from torque by 75%. Also you can use the longest length of the smallest wire possible for that pump, making a reduced voltage soft start that will reduce the torque by 36%.

Also, there are ways to make a torque arrestor with flat blades that are restricted by the water to reduce the spinning action.

However, when you said the pipe was "deformed" that makes be think heat is involved instead of torque. Running a pump too close to its shut off pressure can make the water get hot and "deform" the pipe and fittings.

 

[Sponsor]

 

[Reach4]

Maybe support the pump with something more rigid, taking some torque?

Maybe get some schedule 120 or 160 pipe? https://www.deanbennettsupply.com/pipe.html

One or two brass or stainless nipples would survive, but would those just pass the stress up the path? https://www.supplyhouse.com/Brass-Nipples-163000 https://www.supplyhouse.com/sh/cont...rchText=1-1/4"+stainless+steel+welded+nipples

 

[dchurch]

Maybe support the pump with something more rigid, taking some torque?

Maybe get some schedule 120 or 160 pipe? https://www.deanbennettsupply.com/pipe.html

One or two brass or stainless nipples would survive, but would those just pass the stress up the path? https://www.supplyhouse.com/Brass-Nipples-163000 https://www.supplyhouse.com/sh/control/search/~SEARCH_STRING=1-1/4" stainless steel welded nipples?searchText=1-1/4"+stainless+steel+welded+nipples

I did some searching/reading but haven’t been able to find a solution.

I've been using a submersible pump plumbed vertical in a 1700 gal poly tank for almost 20 years. I have zero complaints about the water system except... A few years ago I upgraded from a 3/4 HP pump to 1 HP. Now we are getting cronic torque damage to the submerged PVC plumbing. This will be my 3rd repair in the past 3 years!

The tank is above ground being feed by gravity spring water used for irrigation. The 1 HP pump is suspended vertically by 1 1/4" sch 80 PVC and 2 rope lines tied to a stainless eye-bolt. The 1 1/4" exits the tank through the tank sidewall near its top rim.

I currently have about 4 feet of submerged PVC pipe above the pump with a check valve and a union, then the PVC elbow that exits the tank. The torque caused damage has always occurred between the pump and the union. The first failure was a section of the PVC pipe deformed and split. Last time a male fitting split at the treads. This time it looks like the damage is to where the pipe enters the union. I wouldn't mind having to do the repairs if they weren't so frequent.

I could use some ideas here.

Maybe black poly pipe could handle the torque better than the more rigid schedule 80?
I'm not sure how well the slip fitting would hold up.

I am aware of torque arrestors but don’t see the application with this setup because my pump cooling sleeve is not connected to anything...

I've consider using metal pipe near the pump but fear the torque will simply cause problems further up the line.

Torque only happens when the pump cycles on. Using a Cycle Stop Valve to decrease the cycles by say 75% will also decrease the problems from torque by 75%. Also you can use the longest length of the smallest wire possible for that pump, making a reduced voltage soft start that will reduce the torque by 36%.

Also, there are ways to make a torque arrestor with flat blades that are restricted by the water to reduce the spinning action.

However, when you said the pipe was "deformed" that makes be think heat is involved instead of torque. Running a pump too close to its shut off pressure can make the water get hot and "deform" the pipe and fittings.

_______________________________________________________________________________________
Thanks Guys, I really appreciate the feedback. Your replys got me thinking. I pulled out a sheet of scratch paper and came up with a plan the seems to be a winner. I cut a 6" hole in the top of my 1700 gal tank and suspended 6 feet of 6" PVC into it. That allowed me to use that pipe like a common well casing. I installed the pump and used a expandable torque supressor. I adjusted the pressure switch so it is well below the pump Max.

At least if I have to service the pump again I will not have to climb into the tank again.

 

[Valveman]

I think that was an excellent idea! Now all you need to do is limit the cycling with a CSV, which will also deliver much stronger constant pressure to the house. If you have enough torque to need stabilization like that, then the pump is cycling on and off way too much.

 

[dchurch]

Thanks Valjean I'll definitely look into that. I did some monitoring of the cycles at the hi/low switch and haven't noticed any unusually high cycle rates. But I do know that this new pump motor has significantly more torque when it kicks on than the old smaller unit that it replaced.

The nicest thing is now pulling the pump is a five minute job. It used to take hours to drain the tank, crawl in, work in the dark, then climb out and refill it.

Thanks again!
Dave

 

[Valveman]

and haven't noticed any unusually high cycle rates.

I hear this all the time. "My pump is not cycling much as I only hear it kick on every 5 to 10 minutes or so." That may not seem like much cycling but there are 1440 minutes in a day. A cycle every 5 minutes is almost 300 per day. The cycles add up quickly and is obvious when you have some of the many problems caused by "torqueing" as you are seeing.

 

[Reach4]

A 4 inch pvc would have been better than 6, because it cools the motor better. However with the high flow, its probably fine with 6 inches. It's better cooling than you had in past years.