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Thread: Concerned over Backpressure by Adding a CSV Valve to Existing System

  1. #1
    DIY Junior Member vpr80's Avatar
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    Default Concerned over Backpressure by Adding a CSV Valve to Existing System

    Long story short. Well ran dry in 2010, had it drilled deeper and new pump installed. Now I think that the pump is too big and cycles too often meaning a short lifetime so I am considering adding a CSV valve.

    The well is 360' deep with the water table at approx 150' deep. The new pump is a Grundfos 25-S-30 and feeds a Well-X-Trol 119 Gal Tank that is 4 years old.

    My biggest concern with the CSV is the back-pressure. How can I check or know whether it will be ok?

  2. #2
    Moderator valveman's Avatar
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    That pump will build 130 psi back pressure. Should not be a problem.

  3. #3
    DIY Junior Member vpr80's Avatar
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    Quote Originally Posted by valveman View Post
    That pump will build 130 psi back pressure. Should not be a problem.
    That's it, just build to 130psi and then what happens as the pump continues to run?
    Last edited by vpr80; 02-23-2012 at 12:16 PM.

  4. #4
    Moderator valveman's Avatar
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    That’s it! 3 HP motors need a CSV with a minimum of about 2 GPM to keep the motor cool. So the only time there will be 130 PSI backpressure is when you are only using 2 GPM, or after you stop using water and the pressure tank is refilling at a 2 GPM rate. During these times the 130 PSI backpressure from the CSV makes the pump think it is in a 300’ well where it can only produce 2 GPM.

    When you need 30 GPM, the CSV opens up and lets the pump think it is only 150’ to water, so the pump can produce 30 GPM.

    Backpressure is a good thing. That 17 amp motor will only be pulling about 8 amps when you are using 2 GPM and the backpressure is 130 PSI. Less amps means less electricity and the motor runs cooler. Most importantly, backpressure is what stops the cycling.

  5. #5
    DIY Junior Member vpr80's Avatar
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    Ahhh ha! Ok got thank you!

    One other question, what are some common uses for the three extra ports on the CSV1A? Seems I can use one 1/2" for a pressure gauge, but what do you do with the others?

  6. #6
    DIYer, not in the trades LLigetfa's Avatar
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    Pressure switch would use another port.

  7. #7
    Moderator valveman's Avatar
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    The CSV1A comes with plugs for those ports in case you don't need them. But they are made to attach the pressure tank, pressure switch, and pressure relief valve, the same way as in the picture to the left.

  8. #8
    DIY Junior Member vpr80's Avatar
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    So basically like this, right?

    Name:  CSV1A .jpg
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  9. #9
    Moderator valveman's Avatar
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    That would work. Or you could do it like this, with the pressure relief in the port on the backside.

  10. #10
    General Engineering Contractor ballvalve's Avatar
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    Why on earth would he abandon a 115g tank? Cant you make it work with that so that his pump isnt running for tooth brushing? 2 hp is a lot of pump.

    When I barrell test pumps and close down the valve to near off flow, and I have done several, from 1/2 to 3 HP, I never get a amp drops of more than 1/2 to maybe 2 amps. 1 seems an average.

    I test a lot of motors under and off load, and from 17 amps to 8 amps? I would be looking for a new meter. Now going the other way, overloading a motor can easily make it go from 17 to 36 amps until it smokes or blows the breaker.

    I certainly agree he needs to not cycle that big pump to death, especially if he can't adjust any irrigation, but this little tank has gotta bump his electric bill pretty tall.

    The bad guy is the pump company that rather than SIZE the pump, sold him what made the most profit for them, or what they had left over.
    Last edited by ballvalve; 02-25-2012 at 10:57 AM.

  11. #11
    DIYer, not in the trades LLigetfa's Avatar
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    Quote Originally Posted by ballvalve View Post
    Why on earth would he abandon a 115g tank? Cant you make it work with that so that his pump isnt running for tooth brushing? 2 hp is a lot of pump.

    When I barrell test pumps and close down the valve to near off flow, and I have done several, from 1/2 to 3 HP, I never get a amp drops of more than 1/2 to maybe 2 amps. 1 seems an average.

    I test a lot of motors under and off load, and from 17 amps to 8 amps? I would be looking for a new meter. Now going the other way, overloading a motor can easily make it go from 17 to 36 amps until it smokes or blows the breaker.

    I certainly agree he needs to not cycle that big pump to death, especially if he can't adjust any irrigation, but this little tank has gotta bump his electric bill pretty tall.

    The bad guy is the pump company that rather than SIZE the pump, sold him what made the most profit for them, or what they had left over.
    Again, you're letting your imagination run away. I don't read anywhere in this thread any suggestion that he abandon his existing tank.

    As for a drop in amps, that will vary based on the pump design.

  12. #12
    Moderator valveman's Avatar
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    Yeah I never said to abandon the big tank. I just showed a picture of the CSV1A with a little tank attached. You could just as easily run a pex or any other kind of line from that port to the big tank. Although if the big tank goes bad, I would not go back with that large a tank. Even with a 2 HP the 4.4 gallon tank is enough, and I would go no larger than a 20 gallon size tank. The amount of water and pump run time used strictly for toilet flusing won't add up to two dollars a month, and will probably be made up for by eliminating cycling for other long term water uses. And I know the amps of that 25S30 Grundfos pump will drop from 17 to 8 or even better, because my own 25S20 2HP drops from 12 amps to 4amps when only using 1 or 2 GPM. If the pumps you test are not dropping at least 30% in amps, then either they are a bad design or the thrust bearing is no good.

    Below is just one way to use the CSV1A as a tank cross for larger tanks. The extra ports on the CSV just give multiple possibilities for ways to plumb it in.


  13. #13
    General Engineering Contractor ballvalve's Avatar
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    Now I see the motor is 3HP. Thats a lot of pump.

    As soon as one of you guys posts a video of a good ammeter attached to a 3 HP pump dropping from 17 amps to 8 amps when throttled down from open flow to 2GPM, I'll be a believer. I have tested it, and see no chance of it, no matter the pump "design".

    amps UP - easy on overload. Amps DOWN, hard to achieve. Words are easy - meters don't lie.

  14. #14
    Moderator valveman's Avatar
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    Pump curves don't lie either. If you know how to read a pump curve, you will see that amps decreasing as the flow rate decreases is the normal way a pump operates. Here are links to two videos. One shows a 5HP three phase pump/motor droping from 10 amps to 5 amps as the flow decreases. The other shows a 10HP single phase pump/motor working from 28 to 58 amps, depending on the flow rate. I thought I had one of my 2HP going from 12 to 4 amps, but I can't find it today. I will video it again next week and post it as soon as possible.

    http://www.spatter.net/csv-video/amp...vs-vfd-dsl.wmv

    http://www.spatter.net/csv-video/csv-dsl.wmv

    I only know of a few pumps that do not decrease amp draw with flow rate. The 10GPM Sta-Rite and a 55 GPM F&W are not good designs and do not work properly with a CSV. Those are the only pumps in 20 years that I have found that do not have a good amp drop. Any pumps that do not decrease amps with the flow rate are either badly designed or the thrust bearing is bad. Most pump companies are more concerned with reducing production cost, increasing profits, and building in planned obsolescence than they are with actually building a quality pump. Finding a pump that has the best drop in amps verses flow and using a CSV to reduce the number of cycles is the best way to beat the system. In that way you can triple or quadruple the life of your pump and beat the manufacturers plan for you to purchase a new pump regularly and often.

  15. #15
    In the Trades Tom Sawyer's Avatar
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    Depending on what you read or believe submersible well pumps average from 7 to 10 to 12 to 15 years but......sediment, installation and pump quality all effect pump life and I'm not real sure where those averages come from either. My own Goulds 1/2 - 7gpm has been in the hole close to 30 years now and still works just fine. If I had to guess I would say that the average pump that we pull for replacement is closer to 20 years old. Now if you consider the amount of work that thing has to do day in and day out, I don't think 10 to 20 years is too awful bad especially when you compare it to the other appliances in your home that work a whole lot less. Nothing lasts forever. Oh and.........I sell pumps
    [B]No, plumbing ain't rocket science. Unlike rocket science, plumbing requires a license[B]

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