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Thread: Low pressure in house

  1. #1
    DIY Junior Member Sean Shannon's Avatar
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    Default Low pressure in house

    Please bear with me as I am not well versed in the way of the well... my father, who recently passed away would take care of the water needs at my parents house.

    The well is a shallow well (60ft or so) with a centrifugal pump with a 6.5hp 3-phase motor and a very large vertical bladderless tank (50+ years old). The pump was always prone to cavitation which would ultimately destroy the impeller and so in an effort to minimize this, my father placed a ball valve between the pump and the tank to force some back pressure onto the pump (don't know if this is the "correct" thing to do or not). There have also been any number of times where my father assumed that the tank had become waterlogged, so he would completely drain the tank and re-fill it; there isn't any sort of air control valve on this tank.

    This well feeds 2 houses as well as the irrigation of the 2.5 acres of grape vines. Irrigation doesn't typically happen until the spring/summer months and I do not believe that this is a daily occurrence during that time period.

    It appears the the cut-in is 20lbs and cut-out is 40lbs. I am not sure why the pressure switch is so low, but there may have been a reason for this.

    What would be the best approach to ensuring longevity of the pump as well as increase the water pressure to the two houses? I am open to any suggestions to help ensure that my mother has the water pressure necessary (toilets take forever to fill).

    I will do my best to answer any questions that anyone has.

    Any help or suggestions would be greatly appreciated.



    Sean

  2. #2
    Moderator valveman's Avatar
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    20/40 is pretty low pressure. 40/60 is more common for a house. But a high volume centrifugal pump probably won’t build any more than about 40. If you have the room in the well casing, I would drop in a little HP sub or a shallow jet pump and get some pressure like 40/60 for the houses.

    You could also add a jet pump as a booster. Pick you water from a pipe coming from the big pump, and booster the pressure from 20/0 to 40/60 going to the houses. The problem here is that both pumps will have to run at the same time for you to take a shower.

  3. #3
    DIY Junior Member Sean Shannon's Avatar
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    I agree that the 20/40 is quite low considering typical city water is around 60lbs, but I am not sure of the reasoning for this. I might try to adjust the pressure switch up to 40/60 and see what happens. Would there be any benefit to changing the tank to a bladder tank or would it just be better to adjust the pressure switch and see what happens?

    It is entirely possible that this size pump is simply overkill now as it used to be used for irrigation of a walnut orchard with large impact rotary sprinklers as opposed to a drip system for the vineyard; so there shouldn't be a need for the sheer volume of water that this pump can deliver. If this is the case, should I swap out the centrifugal pump for a jet pump? I will probably need to figure out how many irrigation drip emitters are within the vineyard so I can determine maximum flow rate needed. I would want to stay with 3-phase as we get a break in electricity costs since it is metered for agricultural purposes.

  4. #4
    DIYer, not in the trades LLigetfa's Avatar
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    Quote Originally Posted by Sean Shannon View Post
    I would want to stay with 3-phase as we get a break in electricity costs since it is metered for agricultural purposes.
    You can get single phase 208V between the phases and I don't see how the PoCo would meter it differently.

    I'm sure valveman could design a two pump system where the second pump is in parallel with the first. Keep the big pump at 20/40 and the small one at 40/60. If the small one cannot keep up and the pressure drops to 20, the big one will kick on.

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    Moderator valveman's Avatar
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    Quote Originally Posted by LLigetfa View Post
    I'm sure valveman could design a two pump system where the second pump is in parallel with the first. Keep the big pump at 20/40 and the small one at 40/60. If the small one cannot keep up and the pressure drops to 20, the big one will kick on.
    Yeah that would be easy if you can get two suction pipes down the same well.

    I doubt your big pump will build any more pressure. It is probably designed for high flow at low pressure. If you turn up the pressure switch higher than the pump can build, it will burn up the pump is a very short time.

    Add up your drip requirements. I'll bet you can do the drip and both houses with a lot smaller pump. And LL is right, you can use just two of the three phases for a cheaper single phase pump, and the meter won't know it isn't running on all three phases.

  6. #6
    DIY Junior Member Sean Shannon's Avatar
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    Thanks everyone. Once the funeral is taken care of, I can turn my attention to figuring out the flow-rate requirements, well depth, and static level so I can start figuring out what size pump I need.



    Sean

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    DIY Junior Member Sean Shannon's Avatar
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    I have not taken measurements of the well at this point, but I did count the number of grape vines within the vineyard. It looks like we have approximately 1821 +-10 vines, each with a single emitter. These emitters are rated at 2GPH @ 15PSI; the vineyard currently does not have a pressure regulator. If I did my math correctly, this would mean that our current requirements would be around 3642GPH or 60.7GPM. Does this math work out for everyone else?

    With the limited information that I have provided about the well at this point, is it still feasible to move to a different style of pump to get more pressure or am I now needing to look at other options for the housing water?



    Sean

  8. #8
    Moderator valveman's Avatar
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    Well the emitters will do 2 GPH, so how many gallons per day GPD do the plants need? If the plants need 10 GPD each, that would only take 5 hours of irrigation time. So you could run about four, 5 hour zones in one 24 hour day. That would only take a 15 GPM pump.

    With a 60 GPM pump running 24/7, you could irrigate a vineyard 4 to 5 times larger. I doubt that you will even need 10 gallons per plant everyday. So you could supply a HUGE vineyard with a 60 GPM pump.

    There is no reason you can’t use the pump you have and just run 5 hours or so a day. But if you have to replace that pump, you could do a lot with a 15 or 20 GPM pump on a drip system, you just have to start early and stay late.

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