If I use two pumps in parallel can I increase l/min ?, and is also pressure increased ?

Thread Starter

meowsoft

Joined Feb 27, 2021
468
If I use two pumps in parallel can I increase l/min ?, and is also pressure increased ?
My Pump is 20 liters/min at 5m head and 10 liters/min at 28m head, If I use Two Pump in parallel can I get 20 liters/min at 28m head ?
and Is my water pressure increased ?
 

Thread Starter

meowsoft

Joined Feb 27, 2021
468
I am get confused with water pressure and water flow, if water flow increased it is also water pressure increase ?
Note : two same pump, with same outlet pipe long and size, 20 meters of 3/4" pipe
 

MrSalts

Joined Apr 2, 2020
537
Your flow will increase but pressure will be the same if the pumps are in parallel. Make sure the pumps have some type of check-valve/back flow preventer or you may pump water back down the other pump because no two pumps are ever perfectly equal.

Unknown effect if the pumps are in series because that can become a mess quickly and not recommended unless you have a surge tank between the two pumps and they are essential acting independently.
 

Thread Starter

meowsoft

Joined Feb 27, 2021
468
Your flow will increase but pressure will be the same if the pumps are in parallel.

Unknown effect if the pumps are in series because that can become a mess quickly and not recommended unless you have a surge tank between the two pumps and they are essential acting independently.
Is that mean I can get more liter per minutes ?
 

Thread Starter

meowsoft

Joined Feb 27, 2021
468
Yes, but I edited my previous post. Read the whole new post.
Ok... thanks... Is liter per minute same with water pressure ?
It is with 2x separated 28 meters of 3/4" pipe, I can get weaker pressure than 1x 28 meters of 3/4" pipe ?
 

Thread Starter

meowsoft

Joined Feb 27, 2021
468
Your flow will increase but pressure will be the same if the pumps are in parallel. Make sure the pumps have some type of check-valve/back flow preventer or you may pump water back down the other pump because no two pumps are ever perfectly equal.

Unknown effect if the pumps are in series because that can become a mess quickly and not recommended unless you have a surge tank between the two pumps and they are essential acting independently.
Yes... I have valve, that prevents my water pump flow back
 

crutschow

Joined Mar 14, 2008
27,739
In general, the flow rate should be near the sum of the two, but the maximum pressure would be no higher than the lowest pressure pump (if you want both pumps to be pumping).
 

Reloadron

Joined Jan 15, 2015
6,064
Something else you want to consider. I run two pumps in parallel as you mentioned. Now forgive me because you will see US measures. With a 10 foot head (about 3 meters) each pump will pump about 61 GPM (231 lpm). Each pump has a 1.5" (38mm). outlet so the area of the outlets are about 1.77 inches ^2 (1142 mm ^2). I can't expect both pumps to run into a 1.5 inch diameter pipe and maintain rated flow. I need a pipe with a circular area of at least twice what each pumps outlet area is.

You need to consider the same at your main discharge where both pumps tie in. Just something else to consider if it applies.

Ron
 

Lo_volt

Joined Apr 3, 2014
219
Oooh... ooh...

Let's explain this using the electricity analogy...
It's all about the fields...

meowsoft your does your system have a pressure tank after the pump? Typically a well pump is used to fill the pressure tank for storage. The pump can fill the tank faster than it is used out of the spigot. The pump is controlled by a pressure switch that turns on at low pressure and off at max pressure. If you want more pressure at the spigot, you can change the setting on the pressure switch. If you change that setting, you will have to add some pre-charge pressure to your pressure tank. Usually there is a filler stem, similar to the valve stem on a car tire, that can be used to adjust the pre-charge on the pressure tank. It's empty pressure should be the same as the pressure at the low pressure setting on the pressure switch.

More pressure at the tank will give you somewhat faster flow at the spigot.

If you want to fill the tank faster, then a second pump or a larger pump is needed and as Reloadron noted, possibly larger pipe diameter.
 

Thread Starter

meowsoft

Joined Feb 27, 2021
468
Something else you want to consider. I run two pumps in parallel as you mentioned. Now forgive me because you will see US measures. With a 10 foot head (about 3 meters) each pump will pump about 61 GPM (231 lpm). Each pump has a 1.5" (38mm). outlet so the area of the outlets are about 1.77 inches ^2 (1142 mm ^2). I can't expect both pumps to run into a 1.5 inch diameter pipe and maintain rated flow. I need a pipe with a circular area of at least twice what each pumps outlet area is.

You need to consider the same at your main discharge where both pumps tie in. Just something else to consider if it applies.

Ron
I needs bigger pipe size for outlet ?, it is better to use 1" pipe for outlet ?, 25mm (3/4") diameter = 490mm2, 32mm (1") diameter = 804mm2, about twice sectional area, and also bigger pipe size for inlet ?
Manufacture says each pump outlet and inlet pipe size is 1", but commonly for same pump people use only 3/4"
 

MrSalts

Joined Apr 2, 2020
537
If the cross-section area of your two pumps is much bigger than the common pipe they are both pumping into, that common pipe will be a restriction. If the flow rate of the two pumps is fairly low, the water flow rate into the common pipe will increase as the water from two pumps reach the constriction. If, however, the flow from each pump is quite high, and turbulent flow occurs (instead of laminar flow), the constriction at the common pipe can significantly slow the total flow and the system may not benefit much from the second pump.
 

Thread Starter

meowsoft

Joined Feb 27, 2021
468
If the cross-section area of your two pumps is much bigger than the common pipe they are both pumping into, that common pipe will be a restriction. If the flow rate of the two pumps is fairly low, the water flow rate into the common pipe will increase as the water from two pumps reach the constriction. If, however, the flow from each pump is quite high, and turbulent flow occurs (instead of laminar flow), the constriction at the common pipe can significantly slow the total flow and the system may not benefit much from the second pump.
Ok... I think I needs about twice pipe size as manufacture describe..., is there any maximum liter/min for each pipe size ?, can 1" pump have 100 liter/min, is there any limit ?
 

drc_567

Joined Dec 29, 2008
1,154
https://www.dutypoint.com/friction-head-loss-2020
The calculator link here gives the head loss due to interior pipe friction, at a specific flow rate (20 l/min.).
For the approximate quantities stated in the above posts, for steel pipe, the head loss is about 2.5 meters, according to the calculator. In order to decrease that head loss, increase the pipe diameter.
... If you were to utilize two identical pumps, producing a flow rate of 10 l/min. each, ideally then, you could produce 20 l/min. at the pipe termination point, and obtain a terminal head pressure of
... 28 m-2.5 m =25.5 m.
... If the pipe is PVC, rather than steel or iron, then the friction head loss would only be about one half of the number given here.
 
Last edited:

MrSalts

Joined Apr 2, 2020
537
Ok... I think I needs about twice pipe size as manufacture describe..., is there any maximum liter/min for each pipe size ?, can 1" pump have 100 liter/min, is there any limit ?
I looked it up...
With 25mm (1") inside diameter, and nominal pressures (below 100psi, you should be able to do about 35 gallons per minute. So 100L/min should be ok.
Water flow gets louder (whistles, vibration) and pressure drops across the length of a pipe if you go over 100psi and flow velocity over 4m/sec. also, water-hammer gets to be an issue so valves should close slowly to avoid metal fatigue.
 
Last edited:

Reloadron

Joined Jan 15, 2015
6,064
I needs bigger pipe size for outlet ?, it is better to use 1" pipe for outlet ?, 25mm (3/4") diameter = 490mm2, 32mm (1") diameter = 804mm2, about twice sectional area, and also bigger pipe size for inlet ?
Manufacture says each pump outlet and inlet pipe size is 1", but commonly for same pump people use only 3/4"
I believe MrSalts covered it well. You look at a pump outlet diameter and calculate the area of the outlet. Using two pumps you really want them feeding a common pipe at least twice the outlet area of a single pump. I only brought this up since you mentioned using two pumps in a parallel configuration.

In my own case I use two pumps with the second pump being about an inch higher in the sump. While a single pump does fine if we get a really heavy rain the second pump comes on. The head on each is well below 10 feet and each pump has a backflow valve so when the first is running I am not backflowing into my sump. What I really need to get done this year is dig up the outside of the house and run the water going into the sump out front to the storm sewer line. In a heavy rain lasting if I lose a pump I am screwed. Each pump is on its own branch circuit too. :)

Ron
 

Thread Starter

meowsoft

Joined Feb 27, 2021
468
I believe MrSalts covered it well. You look at a pump outlet diameter and calculate the area of the outlet. Using two pumps you really want them feeding a common pipe at least twice the outlet area of a single pump. I only brought this up since you mentioned using two pumps in a parallel configuration.

In my own case I use two pumps with the second pump being about an inch higher in the sump. While a single pump does fine if we get a really heavy rain the second pump comes on. The head on each is well below 10 feet and each pump has a backflow valve so when the first is running I am not backflowing into my sump. What I really need to get done this year is dig up the outside of the house and run the water going into the sump out front to the storm sewer line. In a heavy rain lasting if I lose a pump I am screwed. Each pump is on its own branch circuit too. :)

Ron
Ok... do you think it's also good idea to use solenoid valve in inlet pipe ?
Yes... common pipe size is 3/4" but only limited to about 8 meters inlet, and my own is about 7.2 meters, peoples use 3/4" because they can get more pressure, sometimes 1" isn't working, it's only fine with about 2 - 5 meters inlet, do you think 1" inlet pipe size for 2 pumps is enough ?, my borehole case is only 2" size, I was think to use 2x 3/4" for inlet, but 2" case isn't enough big
I think I can use 2x 3/4" for outlet
 
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