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Thread: A stand by Cistern

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    DIY Senior Member Bob1000's Avatar
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    Default A stand by Cistern

    I have a pump system as follows :-
    1HP self priming pump connected to the city mains
    24 Liter pressure tank
    pressure switch set to 40/60
    My system works perfectly in 90% of the time but sometimes in very few seldom occasions the city pressure goes very law for some reason I do not know and in different times of the day as there is no pattern of it at all because sometimes in the peak hour the pressure is good and sometimes it is low at midnight when there is no demand !
    When that low city pressure happens the pump of course can not shut itself off at the 40/60 psi setting the thing that results in continous running of the pump ( I fixed an indicator lamp to show pump is running ) so I have to shut it off manually and watch on the city pressure untill it is back to normal then I reconnect the pump again

    I want to connect a stand-by Cistern ( 250 Liter) parallel to the existing system piping which would enable the pump to pump from it only in those few seldom times of the city low pressure to be able to switch itself off

    Any advice ?
    Thank you all in advance !

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    If you have a self priming centrifugal, it is the wrong pump. They are not made to work with pressure switches. You need either a jet pump or a two stage centrifugal that can make more pressure.

    bob...

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    DIY Senior Member Bob1000's Avatar
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    Quote Originally Posted by speedbump
    If you have a self priming centrifugal, it is the wrong pump. They are not made to work with pressure switches. You need either a jet pump or a two stage centrifugal that can make more pressure.

    bob...
    Then what the self priming pump is made for?
    I have replaced my old 0.75 HP self priming pump by that new 1HP self priming too according to the recommendations of some technicians and I am not able now to replace it again

    I need a stand by water supply anyway because the city water is off few times a week so if you or anybody can advise me how to connect that cistern to my existing system I would be grateful

    Any solutions ?

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    DIY scratch-pad engineer leejosepho's Avatar
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    Quote Originally Posted by Bob1000
    Then what the self priming pump is made for?
    Moving a volume of water from one place to another, such as from one atmospheric-pressure pond or storage tank to another.

    Quote Originally Posted by Bob1000
    Any solutions?
    After the meter, the city line could be teed to add a float switch to fill a cistern, then proceed on (through a check valve) to service the house. Then at the cistern, a pressure pump/tank/switch could also service the house "on demand" though another check valve feeding the supplied line.

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    DIY scratch-pad engineer leejosepho's Avatar
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    PS: It just struck me that you *might* be able to do that with the pump you already have if you run it from a pressure switch set to a pressure just high enough to get at least *some* water when the city system yields none. But, that could lead to a lot of cycling for that large pump.

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    DIY Senior Member Bob1000's Avatar
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    Quote Originally Posted by leejosepho
    Moving a volume of water from one place to another, such as from one atmospheric-pressure pond or storage tank to another.



    After the meter, the city line could be teed to add a float switch to fill a cistern, then proceed on (through a check valve) to service the house. Then at the cistern, a pressure pump/tank/switch could also service the house "on demand" though another check valve feeding the supplied line.
    Ok , but I need to use the water stored in the Cistern only in the time of very low city pressure that would not make my pump reachs 60psi to shut itself off
    Can you explain the piping in more detail please?

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    Sprinkler Guy Wet_Boots's Avatar
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    It might be possible to configure an extra pair of pressure switches to work with these conditions. The low pressure condition that's causing the problem would trip a switch, and that would lock out the existing switch. A second pressure switch with lower pressure settings would take over.

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    DIY scratch-pad engineer leejosepho's Avatar
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    Quote Originally Posted by Wet_Boots
    It might be possible to configure an extra pair of pressure switches ...
    If I have heard correctly, he has city water and the only pressure switch needed in the system would be (or already is) for the "demand-pump backup system" to come on when there is no city pressure.

    Quote Originally Posted by Bob1000
    I need to use the water stored in the Cistern only in the time of very low city pressure that would not make my pump reachs 60psi to shut itself off.
    Correct, but the pump you have cannot get there anyway, right?

    Quote Originally Posted by Bob1000
    Can you explain the piping in more detail please?
    Subject to proper backflow and/or anti-siphon prevention or whatever else might be required, both the city line and the backup system would feed the house through their respective check valves, and some kind of float switch could accept city water to fill your cistern. Then, a pressure switch in the supplied line -- more thought required there -- would trigger your backup system whenever city pressure fell below the best you can get from that pump and a pressure tank.

    So, city water comes in and goes to the house as well as to the cistern, and the backup system also goes to the house when there is no (or very low) city pressure.

    Disclaimer: A real pump man has already said you need a different pump, and I have suggested what I have only because the above is something I would do if I could not afford one.
    Last edited by leejosepho; 06-23-2007 at 01:53 PM.

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    Sprinkler Guy Wet_Boots's Avatar
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    Quote Originally Posted by Bob1000
    Then what the self priming pump is made for?
    I have replaced my old 0.75 HP self priming pump by that new 1HP self priming too according to the recommendations of some technicians and I am not able now to replace it again

    I need a stand by water supply anyway because the city water is off few times a week so if you or anybody can advise me how to connect that cistern to my existing system I would be grateful

    Any solutions ?
    A more careful and exact explanation of your problem might help. Some of your statements don't seem to make complete sense, such as "I need a stand by water supply anyway because the city water is off few times a week" ~ If the water pressure actually fell to zero, you might be hearing advisories to boil your water before drinking. (What city is this?) If all that is happening is that the pressure sometimes is too low for your existing booster pump to raise it to 60 psi, then you can deal with it. The simplest remedy is to buy a pump that can raise the pressure by 60 psi all on its own. A jet pump, for example, or a multi-stage centrifugal. (as already mentioed above)

    Your existing pump might not be good for much more than a 30 psi boost. If you were stuck with using that pump, there might be some pressure-switch trickery that could help. Not help to turn 15 psi into 60 psi, mind you, but to reduce the cutoff pressure to around 40 psi, on a temporary basis.
    Last edited by Wet_Boots; 06-23-2007 at 08:18 PM.

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    DIY scratch-pad engineer leejosepho's Avatar
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    Quote Originally Posted by Bob1000
    I have replaced my old 0.75 HP self priming pump by that new 1HP self priming too according to the recommendations of some technicians ...
    May I respectfully guess those technicians were sales folks at a box store? If so, you might just go talk with the management there and let them know you are willing to forgive the error if you can now swap that pump for the one you actually need.

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    DIY Senior Member Bob1000's Avatar
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    Quote Originally Posted by leejosepho
    May I respectfully guess those technicians were sales folks at a box store? If so, you might just go talk with the management there and let them know you are willing to forgive the error if you can now swap that pump for the one you actually need.
    OK , suppose I could do that , what kind of pump is better ? a 1HP Jet pump or a 1HP 2 stages cintrifugal pump? any specific good trade marks?

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    DIY Senior Member Bob1000's Avatar
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    Quote Originally Posted by Wet_Boots
    A more careful and exact explanation of your problem might help. Some of your statements don't seem to make complete sense, such as "I need a stand by water supply anyway because the city water is off few times a week" ~ If the water pressure actually fell to zero, you might be hearing advisories to boil your water before drinking. (What city is this?) If all that is happening is that the pressure sometimes is too low for your existing booster pump to raise it to 60 psi, then you can deal with it. The simplest remedy is to buy a pump that can raise the pressure by 60 psi all on its own. A jet pump, for example, or a multi-stage centrifugal. (as already mentioed above)

    Your existing pump might not be good for much more than a 30 psi boost. If you were stuck with using that pump, there might be some pressure-switch trickery that could help. Not help to turn 15 psi into 60 psi, mind you, but to reduce the cutoff pressure to around 40 psi, on a temporary basis.

    I have already an RO water filter for the house drinkng and cooking use.

    However , the city pressure never reaches total zero but sometimes is too low to enable my pump to raise it to 60psi to switch itself off

    Also if you think that my pump is only able to produce an extra 30psi pressure boosting to be added to the existing city pressure then the cistern would not help at all because there is no pressure in it only atmospheric pressure and I would difinitly need that new jet or multi stage pump
    Did I reach to the correct conclusion ? please correct me if not
    What is the pressure that jet pump can produce?

    The pressure switch trickery that you are suggesting to reduce the cut off to 40psi would not help at all because its present setting is 40/60 psi and it works fine most of the time obviously because the city pressure is helping it .

    I do need that 40psi as a minimum pressure for the in-line gas bolier to stay on during the shower and to have enough strong water jet from the shower head

    Any other comments apart from changing the pump?

    Thanks

  13. #13
    DIY Senior Member Bob1000's Avatar
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    Quote Originally Posted by leejosepho
    If I have heard correctly, he has city water and the only pressure switch needed in the system would be (or already is) for the "demand-pump backup system" to come on when there is no city pressure.



    Correct, but the pump you have cannot get there anyway, right?



    Subject to proper backflow and/or anti-siphon prevention or whatever else might be required, both the city line and the backup system would feed the house through their respective check valves, and some kind of float switch could accept city water to fill your cistern. Then, a pressure switch in the supplied line -- more thought required there -- would trigger your backup system whenever city pressure fell below the best you can get from that pump and a pressure tank.

    So, city water comes in and goes to the house as well as to the cistern, and the backup system also goes to the house when there is no (or very low) city pressure.

    Disclaimer: A real pump man has already said you need a different pump, and I have suggested what I have only because the above is something I would do if I could not afford one.
    There is only ONE feeding pipe to the house and it passes through the pump system
    In other words , the city pipe feeds the pump inlet and the pump outlet feeds the house
    As per the comment of WET BOOTS here , if my pump woud not be able to raise the city pressure by not more than 30psi , then the Cistern would not be of any good because it is atmospheric pressure !

    Any comments?

  14. #14
    DIY scratch-pad engineer leejosepho's Avatar
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    Quote Originally Posted by Bob1000
    ... what kind of pump is better ? a 1HP Jet pump or a 1HP 2 stages cintrifugal pump? any specific good trade marks?
    I do not know enough about kinds of pumps to answer that question, but SpeedBump has already talked about that and I cannot imagine needing more than 1/2 hp to do what you need.

    Quote Originally Posted by Bob1000
    There is only ONE feeding pipe to the house and it passes through the pump system
    In other words , the city pipe feeds the pump inlet and the pump outlet feeds the house ...
    Understood. A backup system with a cistern would run parallel to that, with the city line also supplying the cistern, and with both city and backup supplying the house.

    Quote Originally Posted by Bob1000
    ... if you think that my pump is only able to produce an extra 30psi pressure boosting ...
    No, that would require a booster pump. As described, the pump you have will only *add* pressure up to a total of about 30.

    Quote Originally Posted by Bob1000
    ... then the cistern would not help at all because there is no pressure in it only atmospheric pressure and I would difinitly need that new jet or multi stage pump
    Did I reach to the correct conclusion ?
    With that particular pump, incoming pressure is irrelevant as long as there is water available ... and that adds another issue to the matter of a cistern backup: pump cutoff when/if the cistern is empty.

    Quote Originally Posted by Bob1000
    I do need that 40psi as a minimum pressure for the in-line gas bolier to stay on during the shower and to have enough strong water jet from the shower head

    Any other comments apart from changing the pump?
    It sounds like that is what it is going to take to resolve your dilemma.

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    Sprinkler Guy Wet_Boots's Avatar
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    Quote Originally Posted by Bob1000
    I have already an RO water filter for the house drinkng and cooking use.

    However , the city pressure never reaches total zero but sometimes is too low to enable my pump to raise it to 60psi to switch itself off

    Also if you think that my pump is only able to produce an extra 30psi pressure boosting to be added to the existing city pressure then the cistern would not help at all because there is no pressure in it only atmospheric pressure and I would difinitly need that new jet or multi stage pump
    Did I reach to the correct conclusion ? please correct me if not
    What is the pressure that jet pump can produce?

    The pressure switch trickery that you are suggesting to reduce the cut off to 40psi would not help at all because its present setting is 40/60 psi and it works fine most of the time obviously because the city pressure is helping it .

    I do need that 40psi as a minimum pressure for the in-line gas bolier to stay on during the shower and to have enough strong water jet from the shower head

    Any other comments apart from changing the pump?

    Thanks
    Change the pump and your worries are over. No trickery required. Looking at the performance curves of the Goulds JS+ shallow-well jet pumps, any of them have shutoff pressures (maximum possible boost) in excess of 60 psi. You just need to match your desired flow rates to the pump horsepower, and make your selection. For a small water supply, say a 5/8 meter on a 3/4 supply pipe, I would probably look at a J5SH pump. Other manufacturers have a similar line to Goulds.

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