A stand by Cistern

Bob1000 · Jun 22, 2007

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 !

Speedbump · Jun 22, 2007

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...

Sponsor · 2022-01-29T12:20:58-0800

Bob1000 · Jun 23, 2007

speedbump said:
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 ?

Leejosepho · Jun 23, 2007

Bob1000 said:
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.

Bob1000 said:
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.

Leejosepho · Jun 23, 2007

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.

Bob1000 · Jun 23, 2007

leejosepho said:
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?

Wet_Boots · Jun 23, 2007

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.

Leejosepho · Jun 23, 2007

Wet_Boots said:
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.

Bob1000 said:
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?

Bob1000 said:
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.

Wet_Boots · Jun 23, 2007

Bob1000 said:
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.

Leejosepho · Jun 23, 2007

Bob1000 said:
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.

Bob1000 · Jun 24, 2007

leejosepho said:
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?

Bob1000 · Jun 24, 2007

Wet_Boots said:
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

Bob1000 · Jun 24, 2007

leejosepho said:
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?

Leejosepho · Jun 24, 2007

Bob1000 said:
... 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.

Bob1000 said:
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.

Bob1000 said:
... 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.

Bob1000 said:
... 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.

Bob1000 said:
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.

Wet_Boots · Jun 24, 2007

Bob1000 said:
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.

Bob1000 · Jun 25, 2007

leejosepho said:
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.

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.

No, that would require a booster pump. As described, the pump you have will only *add* pressure up to a total of about 30.

!

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.

It sounds like that is what it is going to take to resolve your dilemma.

My pump now can reach to 60 psi and shuts itself off in 95% of the time , obviously when the city pressure is enabling it to do so but I am not sure of its value , how you say that it can add pressure up to 30psi only ???
I think there is a missing point of misunderstanding there

Speedbump · Jun 25, 2007

I'll try to make this simple. If your selp primer can make 30 psi all by itself pulling water from a cistern and you were to add 20 psi from the city pressure the way you have it hooked up now, you would have a maximum pressure of 50 psi. 30 from your pump and 20 from the city added together.

Your self primer was made to produce a lot of water at a pressure of between 35 and 45 psi. You don't need a lot of water, you need pressure. A 5/8" meter will give you a maximum of 15 gpm (give or take). A 1/2hp jet pump will produce almost 10 gpm at 40 psi. Pulling out of a cistern that would be a good pump for the home. You would also need a check valve and a tank along with the pressure switch. The 1/2hp pump will make 60 psi with no problem. The cistern in my opinion is the way to go in your situation. By the way, your RO isn't going to work good either with reduced pressure.

bob...

Wet_Boots · Jun 25, 2007

Bob1000 said:
My pump now can reach to 60 psi and shuts itself off in 95% of the time , obviously when the city pressure is enabling it to do so but I am not sure of its value , how you say that it can add pressure up to 30psi only ???
I think there is a missing point of misunderstanding there

If 95% was good enough, you wouldn't be posting here. Have you ever read a pump performance curve? Ever seen one for the pump you now have? Let's say your existing pump can supply a maximum 40 psi boost. If your supply pressure drops below 20 psi, then you can never boost it to 60 psi. The pump won't stop running. A shallow-well jet pump won't have this problem.

Pump Curves The first page is centrifugal pumps, and the second is jet pumps. Jet pumps develop more pressure. They don't deliver as much flow, but that isn't a problem for a single-home booster.

Leejosepho · Jun 25, 2007

Bob1000 said:
My pump now can reach to 60 psi and shuts itself off in 95% of the time , obviously when the city pressure is enabling it to do so but I am not sure of its value , how you say that it can add pressure up to 30psi only ???

As I now see from what SpeedBump has said, I was wrong about the math related to your pump as a booster while considering its possible use with a cistern. A long time ago, someone told me velocities/pressures do not accumulate, but evidently that is not always true.

Bob1000 · Jun 26, 2007

Wet_Boots said:
If 95% was good enough, you wouldn't be posting here. Have you ever read a pump performance curve? Ever seen one for the pump you now have? Let's say your existing pump can supply a maximum 40 psi boost. If your supply pressure drops below 20 psi, then you can never boost it to 60 psi. The pump won't stop running. A shallow-well jet pump won't have this problem.

Pump Curves The first page is centrifugal pumps, and the second is jet pumps. Jet pumps develop more pressure. They don't deliver as much flow, but that isn't a problem for a single-home booster.

Thank you for the information
My pump ( Calpeda ) Italian made and tha catalogue says
Max head is 40 meters
Max discharge 4.2 m3/h

A stand by Cistern

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