centrifugal "sprinkler pump vs. jet pump

Discussion in 'Pumps and Tanks Well Forum & Blog' started by traveller, Jul 21, 2013.

  1. traveller

    traveller Member

    Messages:
    44
    Location:
    British Columbia
    I have a customer who has asked me to install a 3 hp sprinkler pump in the pumphouse above his well. The well is made from a vertical piece of 4' dia. culvert. I measured the distance from the pump intake to the water as 20'. The customer wishes to supply domestic water to a large shop and office plus water to a 1.5" firehose connection installed for the purpose of washing mud from logging equipment; hence, the larger size of the pump. There is a large (15' long) propane tank in the pumphouse that is used as a pressure tank. I assume one of the mechanics there regularly pumps compressed air into this tank to replenish the air volume. I noticed there seemed to be a lot of burned out pumps and pressure switches collected in the back of the pumphouse.

    I am accustomed to installing jet pumps in the 1/2 to 3/4 hp range in wells where the water table is much closer to the surface and have never attempted to install a sprinkler pump as a well pump. The customer requested a cut-in pressure of 40 psi and a cut-out pressure of 60 psi. I connected the pump intake (2") to the 2" suction line there with foot valve and strainer mounted at the bottom. I filled the pump and suction line and observed the water to not be dropping. As a precaution, and to facilitate setting the pressure switch without having to fill the large propane tank, I temporarily installed a smaller (3' diameter) bladder tank on the delivery line from the pump and installed the pressure switch within 2' of it. I then shut the gate valve off that led to the large tank.

    When I turned the pump on, the gauge immediately went up to 45 psi but then very quickly dropped to 22 psi. I assumed it would stay at this pressure for a bit, as the bladder tank filled, and then slowly begin to climb. This was not the case as, long after the bladder tank should have filled, the pressure still stood at 22 psi. I drained the pressure several times and checked to see if the pump was still primed, which it was. When the pump began to get quite warm to the touch, I shut the pump off.

    My question is, am I asking this sprinkler pump to do something it was never designed for? The manual that came with the sprinkler pump claimed that it would pump water from a source 25' below it. If this were true, why would they bother making jet pumps if these sprinkler pumps could do the same job?

    Thank you in advance for any help you can offer.
    Last edited: Jul 21, 2013
  2. leejosepho

    leejosepho DIY scratch-pad engineer

    "A shallow well jet pump can pull water from a maximum of 25’ depth-to-water. Note that it may be less in higher altitudes. In the mountains it could be as little as 18’ to 20’."
    http://www.flotecpump.com/residentialpage_resource_faq_jetpump.aspx

    Altitudes in British Columbia:
    http://atlas.nrcan.gc.ca/data/english/maps/reference/provincesterritoriesrelief/bc_relief/map.jpg

    Altitude might be a factor here, and your description of that overall situation reminds me of customers or employers in my own time who wanted things that were just not going to work well, if at all...and all those "burned out pumps and pressure switches collected in the back of the pumphouse" seem to confirm that in this case also. The presence of that large tank makes me suspicious that two pumps used to be present with one to keep the tank full and another to draw from there for wherever the water needs to go, but then one pump or the other gave out and somebody decided to downgrade the system.
    Last edited: Jul 22, 2013
  3. masterpumpman

    masterpumpman New Member

    Messages:
    729
    Location:
    Virginia Beach, VA
    Wrong pump for the application. Sprinkler pumps don't build pressure and aren't designed for pumping from wells. Suction lifting (one pipe) from 20' is the maximum practical lift for a jet pump.
  4. traveller

    traveller Member

    Messages:
    44
    Location:
    British Columbia
    Leejosepho and Porky

    Thanks for the information, guys. From what I've been reading, I was beginning to suspect this was the answer and you have confirmed my suspicions. Oh, and I forgot to mention the well is located at sea level.

    That being said, do you think this situation would be a good candidate for a jet pump with a two line system and the venturi down in the water at the bottom of the well? As I said, I have never installed this kind of deep well configuration before, as the water tables of the wells I have encountered are usually much closer to the surface.

    This also makes me wonder if it would not be more efficient to place the venturi down in the well in other wells around here, regardless of the depth the water table is at. It does not involve that much more piping, and it would seem to require less energy to pump the same amount of water. Your thoughts on this?

    P.S. Would a "sprinkler" pump and a "centrifugal" pump be the same thing? I noticed, in the collection of burned out pumps, several 5 hp centrifugal pumps; distinguishable by the round bodies of their pumps but lacking the venturi unit on their noses.
    Last edited: Jul 22, 2013
  5. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    3,974
    Location:
    NW Ontario, Canada
    If it were me, I would put a submersible in a sleeve. A sub is twice as efficient.
  6. traveller

    traveller Member

    Messages:
    44
    Location:
    British Columbia
    I have seen that done here. A fellow here made a flow inducing shroud for a submersible pump from a length of 6" PVC drain pipe and a reducing MRJ. (this was also a 4' dia. culvert well) He also had a good depth of water in the well he was working with. Unfortunately, the depth of the water in the well I am dealing with is only 4'. This may sound impossible but, the aquifer is in very coarse (more like small boulders) old beach gravel and the well has almost instant recharge with no drawdown, as is typical of most wells here.

    Considering how much it originally cost my customer for the 4' culvert, and how much it cost him to bring in a large excavator to dig the well, and what a massive hole he must have made trying to dig this deep in beach gravel, I wonder if he would not have been better off to have had a well drilled and a casing and screen installed to begin with. I know, from reading geological surveys, that the hardpan clay is about 35' down at this site and it is solid gravel from the surface to this depth. He might have installed one good submersible pump many years ago and it might still have been running today. Oh well, loggers.....
  7. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    3,974
    Location:
    NW Ontario, Canada
    I've seen sleeves made from a straight section of pipe with a compression style well seal on the top. The seal keeps air from getting in.

    Here is a pic:
    [​IMG]
Similar Threads: centrifugal sprinkler
Forum Title Date
Pumps and Tanks Well Forum & Blog centrifugal start/run switch not engaging Aug 31, 2014
Pumps and Tanks Well Forum & Blog Centrifugal vs jet for pressure boost Jul 18, 2014
Pumps and Tanks Well Forum & Blog Centrifugal sand filter/CSV questions Mar 31, 2014
Pumps and Tanks Well Forum & Blog For Sale: Grundfos Centrifugal Pump with Baldor Motor Mar 29, 2014
Pumps and Tanks Well Forum & Blog confusing data sheet re: centrifugal/jet pump Aug 3, 2013

Share This Page