Hooking Up a Shallow Well Pump

Today, chillums, we will be challenging your rational deductive power.

Picture Lil Missy drinking her soda thru a straw. Yum! Yum! No problemo.

Now take away the straw and replace it with a garden hose. Can she easily suck the soda with the larger diameter of the garden hose the same length as the straw? No she can't!

Therefore, chillums, we know it is easier for a shallow well pump to suck up water with a narrower diameter tube.

AmIright?

It takes more pressure to move a given volume of liquid through a smaller diameter pipe in the same amount of time. It is due to a physical characteristic called conductance.

You may have the wagon before the horse there pardner, we're talking about lifting a narrower column of water up to the point where the pressure is applied.

Are you theorizing or have you tried a water hose as a straw? Given the same length as a straw i think lil missy could do it and empty the glass sooner.

The only comparison I can make is McDonalds. They have (or had, been a while) very big diameter straws compared to other fast food places. It was noticeable (to me) that my drink emptied quicker because of the straw.

Pressure's the same, big pipe, small pipe; depends on the head (height water is raised) not the cross section of the pipe. The pump will just take what it's capacity can handle. What a pump at the top may not be able to do is prime a large pipe and hold that prime when not in use. Primed, it will be happy and run at whatever it's capacity is. A pump at the bottom won't care, it's already primed.

Rufus

@Wayne. Yes, I'm theorizing that a pump rated for a 20' depth with a 1" pipe could draw from 30' with a 3/4" pipe.

Rufus Laggren wrote: depends on the head (height water is raised) not the cross section of the pipe.

I'm hoping that I can increase the pressure at the tap by moving the pump 10' up. I'm thinking that I would have to reduce the inlet pipe diameter so that 30' feet of pipe contains the same weight of water as the original 20'.

Mike Barkley wrote:It takes more pressure to move a given volume of liquid through a smaller diameter pipe in the same amount of time. It is due to a physical characteristic called conductance.

Okay, so the pump would take longer to fill the pressure tank.

>reduce inlet pipe diameter

That's not my understanding how hydraulics works. For a large pipe, the _weight_ of the water in the pipe would be greater if you weighted the pipe and the water - but the _pressure_ would be the same, for the same height in the pipe, no matter the diameter of the pipe.

If you have 12' water sitting in the well, you might be able to get more pressure by pumping from 10' off the bottom instead of from the very bottom. But the well would need to replenish as fast as you pumped because there would be only 2' of draw down before you ran out of water.

"Fresh water: 0.43 psi per foot Sea water: 0.44 psi per foot. So, for each additional 10 feet of depth, figure about 4.3 to 4.4 psi increase in pressure. You can calculate this yourself by using the fact that fresh water weighs about 62.4 pounds per cubic foot (pcf) and sea water weighs about 64 pcf.Oct 27, 2009"

This is a standard hydronic heating calculation because pressure in the system needs to be maintained as low as possible while still reaching the top floors of the building. Eg. 12psi, the default setting for most residential boiler feed regulators, will keep the system happy to about 20',  two stories. Doesn't depend on pipe size at all.

Seems like you would get better results with a stronger pump (more head capacity) and/or a larger pressure tank at the top.


Rufus

Rufus Laggren wrote:

That's not my understanding how hydraulics works. For a large pipe, the _weight_ of the water in the pipe would be greater if you weighted the pipe and the water - but the _pressure_ would be the same, for the same height in the pipe, no matter the diameter of the pipe.

Well maybe I'm amiss on the physics and the diameter of the column of water above the footvalve is arbitrary and a pump would as easily move water from a six inch column as from a one inch column if both were standing 20' above the surface with no drawdown to figure in.

That's my understanding. But if the pump is not at the bottom, priming the larger pipe is not the same as priming the smaller pipe. Once full of water, the pump doesn't care, but until the pipe is full, a pump at the top has to pump air...

Also note that a pump's "usable pressure" or "usable flow" depends on what head it's pumping against in any particular installation. If you must have a certain flow, definitely check the graphs or tables defining the pump characteristics and make sure your installation will do what you plan.


Rufus