Occasional Very law water pressure in the mains

I got my NEW water system as follows
1HP self priming pump connected to the municipality water mains 1" pipe
Pressure tank 24 Liter
Pressure switch set to 50/70 psi
This system works beautifully most of the day but....
It happend few times in summer that the water main has very little water pressure (10psi) to the extend that the pump can not fill the tank and reach to 70psi to shut itself off and keeps running untill i discover that by chance and shut it off manually to keep it from burning out .
How to control this case? I do not like to reduce the setting of the pressure switch to 40/60 psi because when the water pressure in the mains returns back to its normal condition the pump would start cycling during the shower which is fine with the 50/70 setting as the pump keeps running continiously during the shower that way.
I am thinking of one of 2 solutions
1- to fix another pressure switch in parallel to the existing one with low pressures settings say 25/45 psi and change to that one electrically with a 2 way electric switch during the peak hours of the day ( could be done automatically with a 24 hours timer)
2- to fix a low pressue cut off switch in the municipality side ( pumped side) to switch the pump off to protect it thn rings an alarm to switch over manually to the low settings pressure switch

Any other suggestions?
Thank you all very much in advance

You may have bought the wrong kind of pump. A centrifugal is not a very good pressure pump nor does it work well with pressure switches. You should have bought a pump that would make the pressure extremes you want without the assistance of the city pressure. This way it would not be dependent on the city pressure to make the desired pressure.

A multi stage jet pump would have been a better selection. A CSV1/60 or a CSV1Z if you want to experiment, a small tank and your good to go.

bob...

The system should be piped as follows:
City line to the pressure tank and then the pressure tank to the pump.
You should be drawing from the tank and let the city water replace what is being taken this way your pressure should stay constant.

If the city pressure is low, even with a tank on the city side, you will still have to low an inlet pressure for the pump to shut itself off. Of course you will still need another pressure tank on the house side of the pump to keep the pump from banging on and off quickly as the pressure will NOT be constant.

A loss of prime or low suction pressure switch on the pump inlet side will shut the pump down if the city pressure gets low. However, this switch will also shut the pump down when it try's to start as the suction pressure will be lowered momentarily.

Install the low suction pressure switch (reverse acting) on a 3/4" tee with a 1 gallon bladder tank. From the 3/4" tee to the suction line use a length of 1/4" poly or copper tube. This will make a mechanical timer as the water can only get out of the small tank at a certain rate through the small tube. This gives the pump time to get started and the suction pressure back before the switch sees a low pressure and cuts off the pump.

This will only help if the city pressure gets low. Setting your pressure switch that close to the max pressure the pump can build to keep it from cycling is not a good thing. When the pump wears a little, it will not be able to shut itself off no matter the city pressure. All it takes is for you to miss this happening just one time and your pump is toast.

The CSV at 50 PSI constant would be a safer way to keep the pump from cycling, as you can lower the pressure switch to 40/60. This would give you more margin for error from the city pressure as well as the wear on the pump.

Peanut9199 said:

The system should be piped as follows:
City line to the pressure tank and then the pressure tank to the pump.
You should be drawing from the tank and let the city water replace what is being taken this way your pressure should stay constant.

Click to expand...

Where I should fix the pressure switch in this case?

speedbump said:

You may have bought the wrong kind of pump. A centrifugal is not a very good pressure pump nor does it work well with pressure switches. You should have bought a pump that would make the pressure extremes you want without the assistance of the city pressure. This way it would not be dependent on the city pressure to make the desired pressure.

A multi stage jet pump would have been a better selection. A CSV1/60 or a CSV1Z if you want to experiment, a small tank and your good to go.

bob...

Click to expand...

What is CSV1/60 and CSV1Z ?

valveman said:

If the city pressure is low, even with a tank on the city side, you will still have to low an inlet pressure for the pump to shut itself off. Of course you will still need another pressure tank on the house side of the pump to keep the pump from banging on and off quickly as the pressure will NOT be constant.

A loss of prime or low suction pressure switch on the pump inlet side will shut the pump down if the city pressure gets low. However, this switch will also shut the pump down when it try's to start as the suction pressure will be lowered momentarily.

Install the low suction pressure switch (reverse acting) on a 3/4" tee with a 1 gallon bladder tank. From the 3/4" tee to the suction line use a length of 1/4" poly or copper tube. This will make a mechanical timer as the water can only get out of the small tank at a certain rate through the small tube. This gives the pump time to get started and the suction pressure back before the switch sees a low pressure and cuts off the pump.

This will only help if the city pressure gets low. Setting your pressure switch that close to the max pressure the pump can build to keep it from cycling is not a good thing. When the pump wears a little, it will not be able to shut itself off no matter the city pressure. All it takes is for you to miss this happening just one time and your pump is toast.

The CSV at 50 PSI constant would be a safer way to keep the pump from cycling, as you can lower the pressure switch to 40/60. This would give you more margin for error from the city pressure as well as the wear on the pump.

Click to expand...

The city line pipe diameter is 1" , shall I use 1" T?
how long is the length of that 1/4" copper pipe?
what is the rate of that low pressure switch( reverse acting) ? are there different rates for it or you can adjust it to any rate ? is it Square D also?

Use a 1" tee in the suction line. Bush it down to 1/4". You’ll need a 1/4 pipe X 1/4 flare or compression to copper tube. 1" of the 1/4" copper tube is enough to restrict the flow but, 10' of tubing won’t hurt anything. Depends on where you need it to go. Other end of tube you need a 1/4" copper to 3/4" pipe thread. Attach this fitting to a 3/4" threaded tee along with a 1 gallon bladder tank and the switch. You will also need a 1/4 X 3/4 bushing for the switch, and you can use a 1/4 tee there to affix a suction pressure gauge. Square D makes a loss of prime or reverse acting switch. I don’t have the model number handy but, they are fairly common. Loop the control wires from the main pressure switch through this switch as well, so both switches must be made to start the pump. Set this switch for about 10 PSI more than your pump needs on the inlet to achieve shut off on the main pressure switch.

valveman said:

Use a 1" tee in the suction line. Bush it down to 1/4". You’ll need a 1/4 pipe X 1/4 flare or compression to copper tube. 1" of the 1/4" copper tube is enough to restrict the flow but, 10' of tubing won’t hurt anything. Depends on where you need it to go. Other end of tube you need a 1/4" copper to 3/4" pipe thread. Attach this fitting to a 3/4" threaded tee along with a 1 gallon bladder tank and the switch. You will also need a 1/4 X 3/4 bushing for the switch, and you can use a 1/4 tee there to affix a suction pressure gauge. Square D makes a loss of prime or reverse acting switch. I don’t have the model number handy but, they are fairly common. Loop the control wires from the main pressure switch through this switch as well, so both switches must be made to start the pump. Set this switch for about 10 PSI more than your pump needs on the inlet to achieve shut off on the main pressure switch.

Click to expand...

Do you mean that if the pump needs a city pressure of 15psi minimum to be able to achieve a shut off pressure of 55psi then I should set the other low pressure switch cut off to say 20psi ? does that mean that if the city pressure fall to 20psi the pump woul not start ?

Bob1000 said:

[/B][/U]
does that mean that if the city pressure fall to 20psi the pump woul not start ?

Click to expand...

That is correct!

Different Pump Types

I am really mixed up now!
What is the difference between the multi stage pump and the self priming pump and the jet pump with tricked jet?

I am willing to change the self priming pump I bought to a multistage if that one will overcome the problem of the big fluctuation in the city water pressure
I have readjusted the pressure switch down to 40/60 psi any yet the pump could not switch itself off during the peak hours of high demand on water in the city hence the substantially low city pressure

Please explain what the multi stage would do in that case

The more stages a pump has, the more pressure it builds. A jet in a pump will also increase the pressure. You need a pump that can build enough pressure to shut itself off, without counting on any incoming pressure. However, you still need some incoming pressure to feed the pump. In other words, no matter how much pump you have, you can’t draw more water than the incoming line will give you.

You can install a shallow well jet pump with a decent size pressure tank to meet your requirements. You must figure out what those requirements are.

This thread seems like deja vu from a couple of months ago. I don't recall where you are but you are either the same person or are on the same municipal water supply system.

A shallow well jet pump can be selected to comfortably deliver 60 psi while lifting water from 20 feet down in a well or sucking it out of a small pipe. Because of the small inlet pipe, I would install the smallest pump that would meet the demand.

I am going to suggest one pump to discuss, but if it doesn't do what you need, we can pick another one. I am going to select the Goulds J7S from my catalog.

That pump will deliver 70 psi above the inlet pressure when the suction lift is 5 feet (or about -2psi). It will deliver 82 psi at shutoff when the suction pressure is 10 psi. It will deliver 18 GPM at 40 psi when there is -2 psi at the inlet and 6.6 GPM at 60 psi under the same conditions.

I have figured out a control switch setup that will start the pump at 50 psi, and turn it off when the pressure reaches 70 psi or the flow drops to 2 GPM (or some other setting that you choose), whichever comes first. That control will let you get 70 psi when water is available and will protect the pump by shutting it off if the municipal supply is inadequate to allow it to achieve 70 psi. A time-delay relay will also be required to prevent restarting the pump immediately if it shuts off due to inadequate supply on the suction side.

The system should be installed with a good size bladder tank (60 to 119 gallons, depending on space, money, and needs). The tank performs two functions.
1. It stores water for periods when the municipal supply is lacking.
2. It maintains some supply during the "time-delay period" described above.

An alternative to the more complex control system would be a cistern to collect the municipal water, and a jet or multistage pump to provide the required pressure from the cistern to a smaller pressure tank.

I would choose the cistern if space is available, for the following reasons.
1. More storage than a pressure tank if both are the same size
2. Eliminates the variability and control complexity required by the variable delivery of the municipal supply
3. Eliminates the possibility of vacuum on the inlet line, which creates a hazard of in-leak of contaminated water.

It was me but different system

Bob NH said:

You can install a shallow well jet pump with a decent size pressure tank to meet your requirements. You must figure out what those requirements are.

This thread seems like deja vu from a couple of months ago. I don't recall where you are but you are either the same person or are on the same municipal water supply system.

A shallow well jet pump can be selected to comfortably deliver 60 psi while lifting water from 20 feet down in a well or sucking it out of a small pipe. Because of the small inlet pipe, I would install the smallest pump that would meet the demand.

I am going to suggest one pump to discuss, but if it doesn't do what you need, we can pick another one. I am going to select the Goulds J7S from my catalog.

That pump will deliver 70 psi above the inlet pressure when the suction lift is 5 feet (or about -2psi). It will deliver 82 psi at shutoff when the suction pressure is 10 psi. It will deliver 18 GPM at 40 psi when there is -2 psi at the inlet and 6.6 GPM at 60 psi under the same conditions.

I have figured out a control switch setup that will start the pump at 50 psi, and turn it off when the pressure reaches 70 psi or the flow drops to 2 GPM (or some other setting that you choose), whichever comes first. That control will let you get 70 psi when water is available and will protect the pump by shutting it off if the municipal supply is inadequate to allow it to achieve 70 psi. A time-delay relay will also be required to prevent restarting the pump immediately if it shuts off due to inadequate supply on the suction side.

The system should be installed with a good size bladder tank (60 to 119 gallons, depending on space, money, and needs). The tank performs two functions.
1. It stores water for periods when the municipal supply is lacking.
2. It maintains some supply during the "time-delay period" described above.

An alternative to the more complex control system would be a cistern to collect the municipal water, and a jet or multistage pump to provide the required pressure from the cistern to a smaller pressure tank.

I would choose the cistern if space is available, for the following reasons.
1. More storage than a pressure tank if both are the same size
2. Eliminates the variability and control complexity required by the variable delivery of the municipal supply
3. Eliminates the possibility of vacuum on the inlet line, which creates a hazard of in-leak of contaminated water.

Click to expand...

Hi Bob
It was me yes but have changed my old ystem according to the suggestions of the members here but I still have the problems that I mentioned above
The space is available in my garden for a cistern ( what size you suggest?) so please give me much more details in that direction because I also agree with you or in fact very worried about leak-in contaminated water because of the momentary vacume in the inlet pipe
Thank you in advance

The size of the cistern depends on your usage and the reliability of the source. For example, if you can only depend on 5 liters per minute from the municipal supply, but you need 1000 liters in a peak hour, then you need at least 700 liters of storage available. With a little allowance for safety, you might get a 1000 liter plastic tank.

The fill control can be simply a float valve. They are similar to the old "toilet tank" valves but are available in larger sizes. You can see them at www.grainger.com; stock numbers 2X524 or 2X525 would do the job. They are Watts ST500 and ST750.

Then you can use a shallow well jet pump (or a multistage centrifugal) with bladder tank to meet your flow and pressure needs. You can select a jet pump, bladder tank, and pressure settings to minimize cycling during steady demand periods. The bladder tank should have an actual volume at least 3 times the nominal flow rate of the pump.

If a bladder tank is not available where you are, you can use a standard tank without a bladder but you will have to provide air makeup.

If the supply is not reliable, you should put a float switch in the cistern to shut off the pump if it runs low on water.

You should start by figuring out the demand peak short flow liters per minute, peak 10 minute period, and peak hour. That and the source capacity are enough to let you select the pump, pressure tank, and cistern.

Come back if you need more information.

Without a cistern, if the city pressure is fairly high, say 40 PSI, when that J7S pump comes on at 50 PSI, it will be trying to pump 20+ GPM to fill the pressure tank. That is probably more than the inlet pipe can supply, which will shut the pump off on low suction pressure. A time delay on the low suction pressure switch, will do the same thing as the small tank and 1/4" line attached to the low suction pressure switch. Either way it will delay the pump from going off for a certain time, after the suction switch has opened. The pump is still running during this delay, so the large pressure tank is not needed to maintain some supply during the time delay period.

I would use a very small pressure tank (actual 2 gallon size) with a 60 PSI Cycle Stop Valve. In this way when the pump comes on, the CSV will only allow the pump to supply the same amount of water that is being used, instead of 20+ GPM into a pressure tank. This will keep the pump from drawing more water to fill a large pressure tank than the inlet line can supply. Even when the city supply pressure is almost 0 PSI, this pump will still deliver 6.6 GPM at 60 PSI. This should be more water than the house will ever need. With the CSV and small tank, the pump will never draw more water than is actually being used, so the draw on the supply line will never be more than it can supply.

Also the CSV will keep the pressure at a constant 60 PSI instead of it letting the pump cycle on and off between 50 and 70 PSI while you are in the shower.

I would also use a J10S instead of the J7S. The J7S can only build 70 PSI. If the city pressure is 0 PSI, or if you are using a cistern, the J7S cannot build enough pressure for a 50/70 pressure switch. The J10S can build 74 PSI, which can easily shut itself off at 70 PSI.

If the city never completely runs out of water, just has low pressure, this set up will be all that is needed. If the city does sometimes run completely out of water, the cistern set up would be better.

The same pump set up described above will work with or with out a cistern. This will allow you to first try the pump set up connected directly to the city supply. The low suction switch will keep you from having to worry about drawing a vacuum on the suction line. Then if the city ever runs completely out of water, you could easily add the cistern with a float valve. With an extra tee and a couple of ball valves, you could have the pump already set up to close off the city to the suction of the pump, and open a suction line to the cistern.

It sounds like the city can supply enough water, just not enough pressure. In that case the cistern would not be needed. If it is not needed, the cistern is just another place for the water to get contaminated. Drawing from the cistern will also increase the power consumption as you are losing what pressure is coming from the city. The pump will use more energy building the pressure up from 0 PSI from a cistern, than from 20 or 40 PSI from the city line.

The J7S was suggested for the case of "suction connected to the municipal supply". It was suggested based on two considerations:

1. Provide enough pressure margin to get to 70 psi when there is enough water available.
2. Minimize the overpumping on the 1" line when the supply is inadequate.

The cistern concept is to provide something that is sure to work, because the previous approach used in response to suggestions from this board didn't work. (I didn't try to find those suggestions.)

I did not suggest that the J7S should be used with the cistern system. If a cistern is used, then the pump must provide more pressure because there is no pressure from the source.

The jet pump, tank with a volume at least 3 times the mid-range GPM of the pump, and pressure switch switch shutoff high enough to limit the GPM, will let the pump run without cycling during times of high demand.

You asked what the CSV's were. They are Cycle Stop Valves that will keep the pump from cycling and taking itself out and for providing constant pressure to your home. With the correct pump they work great.

bob...

Again a big pressure tank will cause the pump to deliver 20+ GPM just to refill the pressure tank and the supply line will probably not deliver that much. Also the pump will still cycle at low flow rates. You said, and I agree, that the pump should not cycle while you are taking a shower. The small pressure tank and CSV will not let the pump cycle while a single shower is running, and it won't over pump the feed line while filling a large pressure tank. There really is no need for a large pressure tank. If you need to store water, use a cistern.

I think I might need to go for the cistern

Present situation now is :-
I have reduced the pressure switch settings to 40/60psi , the pump would hardly switch itself off in the noon time (obviously the time of heighest demand) but today I fixed a pilot lamp in the kitchen which goes on when the pump is running and to my surprise that the pump at certain point of the noon time could not shut off so I had to disconnct the main switch!
After some time I switched on the main switch and the pump could fill the tank and switch itself off.
In the evening I had a shower but the pump kept cycling during the shower ( not that much but it did ) while that cycling phenomina was not there when the pressure switch setting was 50/70psi

Now I do not know what to do to , obviously the CSV would not work in my case because it would make it more difficult for the pump to switch off in the time of low city pressure

I was trying to avoid the cistern concept but it seem that it would be the best thig in my case!

Any comments?