Author Topic: CSV use in uphill climb to house and reduced pressure backflow preventer  (Read 143 times)

Starship49a

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I just built a new well house and my bladder tank recently failed so it seems a good time to consider all options before  moving the “system” into the new well house.  Here are the basics:  my well is 520 ft deep, the pump is at 460 ft and the static level is 395 ft.  My pump is a 240 volt, 2 HP, 10 gpm Sandhandler.  The new well house is 15 ft from the well and the pipe from the well is 1 1/4” and a dedicated input to the tank, (ie., no tee’s or other connections.). The new system will have two dedicated output’s:  a 176’ - 1 1/4” line to the house climbing 15 ft in elevation and a second dedicated line going through a reduced pressure backflow preventer to all the yard hydrants and irrigation systems on our 5 acre farm.  After the tank the line runs through a sediment filter, an iron/sulfate filtration system and a water softener before branching off to the dedicated house and “yard” systems.  I live in western Nevada and the water temperature exiting the well is a balmy 70 degrees and reaching upper 70’s before it make the uphill trek to the house; a perfect growing medium for iron bacteria and sulfates resulting in stinky water.  The less water sitting in a warmer well house the better so the CSV and small tank may have some real advantages.  I have 4 questions:
1.  Is the CSV pressure adjustable?  I will lose 7 1/2 psi going up the hill to the house.
2.  Is there any issue with running the CSV system through the reduced pressure backflow preventer?
3.  I have read many of your explanations on how the CSV works and am pretty familiar with centrifugal pumps as a retired fire engineer.  What I do not understand is the “soft start.”  If the pressure tank starts the pump when it hits the start up pressure, say 40 psi, doesn’t it slam the pump into gear as normal?
4.  Finally, if the CSV limits the line pressure to 50 psi, how does the pressure tank reach the shut off pressure of 60 psi?

Cary Austin

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Answers in bold.

I just built a new well house and my bladder tank recently failed so it seems a good time to consider all options before  moving the “system” into the new well house.  Here are the basics:  my well is 520 ft deep, the pump is at 460 ft and the static level is 395 ft.  My pump is a 240 volt, 2 HP, 10 gpm Sandhandler.  The new well house is 15 ft from the well and the pipe from the well is 1 1/4” and a dedicated input to the tank, (ie., no tee’s or other connections.). The new system will have two dedicated output’s:  a 176’ - 1 1/4” line to the house climbing 15 ft in elevation and a second dedicated line going through a reduced pressure backflow preventer to all the yard hydrants and irrigation systems on our 5 acre farm.  After the tank the line runs through a sediment filter, an iron/sulfate filtration system and a water softener before branching off to the dedicated house and “yard” systems.  I live in western Nevada and the water temperature exiting the well is a balmy 70 degrees and reaching upper 70’s before it make the uphill trek to the house; a perfect growing medium for iron bacteria and sulfates resulting in stinky water.  The less water sitting in a warmer well house the better so the CSV and small tank may have some real advantages.  I have 4 questions:
1.  Is the CSV pressure adjustable?  I will lose 7 1/2 psi going up the hill to the house.
Yes the CSV1A is adjustable from 15 to 150 PSI.

2.  Is there any issue with running the CSV system through the reduced pressure backflow preventer?
No, but you will lose another 10 PSI through an RPZ, adding to the 7.5 from the elevation.  You need to use a 60/80 pressure switch setting and the CSV at 70 to get 50 PSI up the hill and through the RPZ.  With a 2HP pump and a 60/80 pressure switch you should use at least a 20 gallon size pressure tank.  At the 60/80 pressure it will only hold about 3 gallons of water.

3.  I have read many of your explanations on how the CSV works and am pretty familiar with centrifugal pumps as a retired fire engineer.  What I do not understand is the “soft start.”  If the pressure tank starts the pump when it hits the start up pressure, say 40 psi, doesn’t it slam the pump into gear as normal?
There are several ways to make a soft start.  The best way is to not oversize the wire.  Using the longest length of the smallest wire possible for the HP pump you are using, will give a reduced voltage soft start.  A motor can't start hard if it can't get the extra amps.  This doesn't effect the performance, but reduces starting torque by like 36%. 

Starting a pump against a closed or almost closed valve also makes the pump start softer, greatly reducing the duration of inrush current.

Either one of those is good, using both is even better.  There are many advantages to this over using an electronic soft start or VFD.



4.  Finally, if the CSV limits the line pressure to 50 psi, how does the pressure tank reach the shut off pressure of 60 psi?
The CSV just cannot completely close.  It is that simple.  When you stop using water there is still 1 GPM leaking through the CSV that now has no place to go except into the pressure tank.  At 1 GPM the CSV fills the tank from 50 to 60, or in your case 70 to 80 PSI and the pressure switch shuts off the pump.


Starship49a

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Thank you for the detailed responses.
I do not plan to run the house line through the RPZ, only the yard system.  Running the CSV At 70 as you suggested would then make the house pressure a constant 60-63 which would be nice I think.
My 460’ of wiring down the casing is 8 gauge; would you consider that as oversized and affecting the soft start?  The reason I ask is because my 2HP pump’s power curve notes it should be providing 10 gpm at 450’ @ 36psi.  I am only getting 7 gpm at 36 psi and 5-6 gpm at 50 psi, so at 9 years old my pump may be starting to weaken.  If I have to replace the pump it would be a logical time to change the wiring to assist with a softer start.  Your thoughts?

So far I am tracking with you, but I have a question on low volume intermittent water use and how it plays out with the quicker tank draw down.  My wife and I are the only 2 people living in our home and many of our water uses during the day are a toilet flush, quick hand washing and a glass of water or a pot of coffee.  None of these by themselves would cycle the pump even with the small tank...but of course I realize that will occasionally be the case.  (We live in the desert so have no irrigation)  And it is a given that showers/baths will work excellently with the CSV.  The other big user of water is the washing machine.  As luck would have it, our HE washer is dying just like the bladder tank so I am glad actually.  With the HE method of spritzing the hot water in and a tankless water heater a fair distance away from the washer, we can never really get a hot laundry load.   I am actually thinking an old fashioned washing machine that  fills the tub For the wash and rinse cycles might work better with the CSV Than an HE washer.  (I know it would be better at getting hot water in at one time rather than intermittently). What do you think?
« Last Edit: August 23, 2020, 08:20:44 PM by Starship49a »

Cary Austin

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Yeah you will like 60 PSI at the house.

With a total length of 390' of #10 wire or 620' of #8 the motor will get a soft start.  You can either add another 160' of #8 wire, or you can use 390' of #10 wire from the pump up and splice to the #8 wire from 390' to the surface.  You are only 160' short of the longest length of #8 wire, so it will give you some soft start as it is.

Pumps don't usually wear out gradually unless you are pumping sand or sediment?  They usually pump what the curve says until the day they die.  Even from 450' and 36 PSI that pump should be doing 10+ GPM.  You maybe just getting all the water the well can produce.  If the pump starts out at 12+ GPM then drops off, the pump is fine and the well is the problem.  If the pump starts out at 5-6-7 GPM, the pump is the problem.

It doesn't hurt anything if your pump cycles on for every toilet flush.  The CSV doesn't let it do that but it still wouldn't hurt.  On average the small tank makes the pump cycle 10-15 times a day total, no matter how many times you flush and wash hands.  Taking out all the repeated cycling like for long showers and irrigation is what makes the pump last.  It is also better to have water fresh from the well at a strong constant pressure, no matter how much or how little water you are using.  With a big tank the pump may only cycle once for small uses, but the water is sitting in a rubber bag all day and is delivered at an ever decreasing pressure as the tank empties.

Those washing machines that "spritz" the water every so often are terrible.  They cause tremendous water hammer opening a closing that solenoid valve like that.  However, if the "spritz" every 60 seconds or so the CSV will keep the pump running the entire time when using the 10 gallon size tank.  With the CSV tanks are more a mechanical timer than for water storage.  It takes over 60 seconds to fill the last half of a 10 gallon size tank, so your pump will run at least 1 minute before shutting off.  If the washer "spritzes" in less than 60 seconds the pump never shuts off until the load is done.