Pumping from a Cistern

[MikeInTN]

Hi, I’m new to the forum after lurking for some time.  I spoke with someone very helpful in your office last week – Sam – but have a few follow-up questions I wanted to post and thought it might prove useful to others who may encounter a similar situation.  After a couple of failed attempts with low producing wells, I am having a spring developed that produces ~7gpm.  This spring will be feeding a 1200-gallon cistern buried a few feet below the source of the spring.  I purchased a Hallmark Industries MA0414X-7A [230V 2-wire] submersible pump.  Pump will be mounted in a 4” flow inducer sleeve and mounted horizontally on top of two 4” PVC pipes as I’ve seen pictured elsewhere here on your forum.

This set-up, initially, will be supplying a single-story home located ~70 feet above the cistern, with a horizontal distance of [I’m guessing] 350 feet.  The person developing the spring and installing the tank is burying 1½” PVC and 10-3 wire.  I could’ve used 10-2 but I didn’t know at the time what pump I would be using.  I want to use the PK1A Pressure Tank Kit with the 10-gallon tank, 40-60 pressure switch, with the CSV setting of 50psi.  The pressure tank and CSV will be located at the house, and not at the cistern so that I can weather/critter-proof them. 

Most of the discussions posted here relate to using wells as the water supply, so I’m not sure how things like maximum head and backpressure come into play when pumping from a cistern.  Could you comment on this set up?  Also, I’ll need to install a 1¼” nipple, check valve, and 90* elbow on the pump, and I’m curious what you used in your example picture [the one with the horizontal installation] – brass, stainless, galvanized?  On the flow inducer sleeve, would 4” pipe give enough flow around the motor for cooling?  My pump is listed as having a max diameter of 3.8”, but I think that includes the bump out for the wiring.  Is SDR35 safe for drinking water or would you use PVC in that case?  Do you use or recommend anything to center the pump in the sleeve, such as bolts spaced at 120*?  Anything else I should be concerned about?

Thanks in advance,

MikeInTN     

[Cary Austin]

Hi, I’m new to the forum after lurking for some time.  I spoke with someone very helpful in your office last week – Sam – but have a few follow-up questions I wanted to post and thought it might prove useful to others who may encounter a similar situation.  After a couple of failed attempts with low producing wells, I am having a spring developed that produces ~7gpm.  This spring will be feeding a 1200-gallon cistern buried a few feet below the source of the spring.  I purchased a Hallmark Industries MA0414X-7A [230V 2-wire] submersible pump.  Pump will be mounted in a 4” flow inducer sleeve and mounted horizontally on top of two 4” PVC pipes as I’ve seen pictured elsewhere here on your forum.

This set-up, initially, will be supplying a single-story home located ~70 feet above the cistern, with a horizontal distance of [I’m guessing] 350 feet.  The person developing the spring and installing the tank is burying 1½” PVC and 10-3 wire.  I could’ve used 10-2 but I didn’t know at the time what pump I would be using.  I want to use the PK1A Pressure Tank Kit with the 10-gallon tank, 40-60 pressure switch, with the CSV setting of 50psi.  The pressure tank and CSV will be located at the house, and not at the cistern so that I can weather/critter-proof them. 

Most of the discussions posted here relate to using wells as the water supply, so I’m not sure how things like maximum head and backpressure come into play when pumping from a cistern.  Could you comment on this set up?   That pump builds a max head of 207' or 89 PSI.  You are going to lose 30 PSI of that in the 70' of elevation from the cistern to the house.  That means you will only have 59 PSI available at the house.  That won't work with a 40/60 switch.  You can just barely do a 30/50 switch setting with that pressure.  With 70' of elevation after the cistern it is like having a 70' deep well, and you need a smaller GPM series pump that can produce more pressure.  Those pumps work fine when the cistern is at house level.

Also, I’ll need to install a 1¼” nipple, check valve, and 90* elbow on the pump, and I’m curious what you used in your example picture [the one with the horizontal installation] – brass, stainless, galvanized?  Any of those will work. Make sure to use a metal, spring loaded, check valve and if you use any galvanized nipples or fittings be sure and wrap them completely with electric tape.


On the flow inducer sleeve, would 4” pipe give enough flow around the motor for cooling?  My pump is listed as having a max diameter of 3.8”, but I think that includes the bump out for the wiring.  Is SDR35 safe for drinking water or would you use PVC in that case?  PVC pipe is PVC pipe no matter if labeled for drinking water or not.  Yes that should include the cable guard, but even so will have plenty or room for over 25 GPM flow.

Do you use or recommend anything to center the pump in the sleeve, such as bolts spaced at 120*?  Anything else I should be concerned about? Wont hurt to just lay the pump in the sleeve.  No centering is needed.

Thanks in advance,

MikeInTN   

[MikeInTN]

Cary,
Thanks so much for your response.  I have some updated information regarding the pump height from the cistern.  Maybe not the best method, but I used 4 different devices [2 cell phones using triangulation and 2 Fitbits measuring floors climbed] and got an average pump height of 52.9’.  Using your previous calculations with my pump with a max head of 207’ (or 89psi), my psi lost would be 52.9’/2.31 = 22.9, with 66.1 psi available at the house.  Is that correct?

I’m not sure if I will be able to return the pump I just bought.  If not, would it be acceptable to use with a 30-50 pressure switch and a CSV setting of 40?  Would the adjusted numbers allow use of a 40-60 pressure switch, or is it still too marginal?  If I can return it, I’m looking at a slightly smaller Hallmark MA0460X-9A pump with max head of 240’.  Would that be a better option?

MikeInTN

[Cary Austin]

You are figuring correctly.  But 66 PSI max is just too close to work with a 40/60 switch.  Yes it would work fine at 30/50, but I don't think you will like the pressure.  I didn't know that other pump was available, but yes because of your 53' rise in elevation that pump would be better and work fine at 40/60.

[MikeInTN]

So my new pump arrived today.  It's the Hallmark MA0460X-9A.  My last concern is backpressure on the pipe between the pump and the CSV since it will be buried in a trench and not easily accessible.  Would you mind telling me how to calculate the backpressure on the pipe?  I don't know if this is too little/much information. 
Elevation from cistern to house is 53'. 
Total length of 1 1/2" PVC pipe is 350'.
Pump is 1hp, 230V, 5.8amps, 240' max head for open water tanks, 25 gpm (max), 13 gpm (rated)
The CSV I am looking at is the Pside-kick kit with a 10 gallon tank, 40-60 switch, 50psi setting.
My apologies for so many questions.

[Cary Austin]

That pump can do a max dead of 240', which is about 103 psi.  2.31 feet equals 1 psi.

[MikeInTN]

Hi, Cary.

I contacted Hallmark Industries after receiving my pump because the actual specs on the pump did not match the listing on their website.  They kindly responded and told me what I received was the new all stainless steel [including the discharge] version of the pump, MA0460X-9A-DO, 1 hp, 5.2 amps, with a max head of 220’.

So, using the information/formulas you previously provided, this is what I came up with:
-   Pump max head = 220’, or 95.2 psi (max head divided by 2.31) = maximum back pressure on pipe.
-   Pump height/2.31 = 53/2.31 = 22.9 = psi lost
-   PSI available at the house = 95.2 – 22.9 = 72.3
-   Pressure differential between max head and 50psi CSV setting = 95.2 – 50 = 45.2
-   [From the pump manufacturer] Flow at water level of 53’:
           The minimum total head (@40 psi) = 53' + 40 x 2.307 = 145.28'
           The maximum total head (@60 psi) = 53' + 60 x 2.307 = 191.42'
-   Max pumping level to a pressure tank, 40/60 psi switch @60 psi:
           220 – 60 x 2.307 = 81.58’

Can you confirm the calculations/assumptions above look correct, and would this work with the Pside-kick kit with a 10-gallon tank, 40/60 switch, 50 psi setting?

[Cary Austin]

Your close.  After deducting the 22.9 PSI for the 53' of lift, all you have left is 72.3 PSI.  Then working with a 40/60 pressure switch the minimum differential needed is between 60 PSI and the 72.3 PSI.  This only leaves you with 12 PSI differential, which will work, but just barely.  If your water level gets any deeper than 53' the pump may get hot before it gets to 60 PSI and shuts off.