Thread: Well Downpipe Diameter

Hmm, with a 1 inch pipe it is drawing less water but for possibly longer?

You are right, the 2 inch pipe puts more FORCE on the valve but the PRESSURE would be the same as with a 1 inch pipe. Your pump produces underpressure to suck up a column of water and that pressure will remain the same for any column size with the same height. And therefore the pump power required will remain the same too.

What does affect you pump performance is disturbance of laminar flow of the fluid,
so do not start with a large diameter pipe and reduce abruptly to a smaller size.

Big pipe small pump
small pipe big pump.

as#3 the pressure is related to head only, big suction pipe less pipe friction.

1" pipe or 10" pipe hydrostatic pressure is the same, gravity...

Use the pipe diameter matching the pumps inlet and outlet holes, the mfgr would had made a 2" hole if that would had been more efficient for his construction.

Use the same diameter as the pump inlet as has been said.

Larger may stay larger longer if there is any build up but on the other hand the higher velocity of the smaller will reduce the likely hood of buildup.

If you have a pump rated for a maximum well depth of 8 meters and you have an infinite amount of water at 5 meters

What size riser pipe will not a problem if it is larger.
You would have a problem if the riser pipe was smaller.
Your flowrate will depend onthe depth of the water you say 5 metres
Maybe but the longer the pump runs without stopping that water level mite drop
This would reduce the flowrate.


http://inspectapedia.com/water/Private_Well_Pressure_Diagnosis.htm

Thanks all for the excellent replies and information. The reason I am asking is that right now I am using a 1 inch downpipe in a 2 inch well casing, but I want to go with a completely sealed well and water system so I am going pull out the 1 inch down pipe and will put a 2 inch to 1 inch adapter on the top of the well casing and go to the pump with 1 inch pipe which is what the pump is configured with. Just wanted to confirm I am not doing something stupid. The well is 8 meters deep and has two meters of spiral slotted well screen at the bottom in water bearing sand and gravel. The water actually comes within 2.5 meters of the surface but I exaggerated those figures to make the question more clear. Thanks again for the help.

Originally Posted by thailazer

The reason I am asking is that right now I am using a 1 inch downpipe in a 2 inch well casing, but I want to go with a completely sealed well and water system

why seal it?

when you are drawing water, something needs to replace the water taken out, and that is usually air

if that becomes impossible, then you will build up negative pressiure in the borehole (unless the water is flowing into the bore easily)

Originally Posted by DrAndy

when you are drawing water, something needs to replace the water taken out, and that is usually air if that becomes impossible, then you will build up negative pressiure in the borehole (unless the water is flowing into the bore easily)

Dr Andy that's rubbish, your sucking from a porous zone, negative pressure?
your sucking, it's not flowing? Replacing with air? New theory?

Originally Posted by DrAndy

Originally Posted by thailazer

The reason I am asking is that right now I am using a 1 inch downpipe in a 2 inch well casing, but I want to go with a completely sealed well and water system

why seal it?

when you are drawing water, something needs to replace the water taken out, and that is usually air

if that becomes impossible, then you will build up negative pressiure in the borehole (unless the water is flowing into the bore easily)

I am sealing it as the water is potable and I don't want any way for bacteria to get in. No storage tanks for me which are always breeding grounds for lots of critters. The negative pressure you mention is impossible as the last I checked, there was lots of atmosphere pushing down on the aquifer!

My two brothers are plumbers and they taught me a long time ago:
"You can't judge the depth of the well by the length of the handle on the pump"

Something I always remembered (for some strange reason)
Also: Shit runs downhill and payday is on Friday.

Good luck with your well (and pump)
I would put in a jet pump system (two pipes to go down to a jet valve)
That's what I have in my home in the states. Works down to 100' (30 m)

The best well system is submersible pumps, it will deliver high pressure in shallow depth well or Deliver water from 90 metres 290ft deep well at a lowwer pressure.

Originally Posted by Airportwo

1" pipe or 10" pipe hydrostatic pressure is the same, gravity...

Corect Answer .

Originally Posted by Airportwo

Originally Posted by DrAndy

when you are drawing water, something needs to replace the water taken out, and that is usually air if that becomes impossible, then you will build up negative pressiure in the borehole (unless the water is flowing into the bore easily)

Dr Andy that's rubbish, your sucking from a porous zone, negative pressure?
your sucking, it's not flowing? Replacing with air? New theory?

as I said, it all depends if the water is flowing easily (read that bit)

if it does not then negative pressure is likely

think about it

if you take out more water than flows in, then there will be a drop in the pressure if the bore is sealed

^ doesn't work for me? if you have negative pressure you have a dry well, even if it's very porous for it to flow or be pumped you have to have pressure greater than hydrostatic.
If you take out more water than flows in, there will obviously be a drop in pressure, if you seal the well bore, close it in, the pressure in the well will rise depending on the flow rate and porosity of the zone?

just imagine you are drinking out of a cardbox fruit drink with a straw

as you suck the drink out, the box will slowly collapse due to negative pressure unless the straw hole is enlarged ( equivalent to the borehole not being sealed)

now imagine the box is in a water container

if the box has small pinholes that collapse will not happen so fast, but it will still happen

that makes it more difficult to suck the drink out due to the negative pressure

if the pinholes are enlarged (equivalent to more water flow going in) then it is easy to suck out the drink

I can kind of see where you are coming from, I have been drilling holes for nearly 40 years and have never heard any body explain pressures quite like you have
All zones where you produce from, be it water, oil gas... naturally breathe as you will always be "producing" from porous formations, having a bore open to the air is immaterial, if the formation psi is .433 psi/ft normally pressured the air will not have the force to enter the formation to replace ?

Dr Andy
I congratulate you. I read this thread the other night and thought how can I easyily explain this situation and now reading your post I know so thanks for teaching an old dog a new trick.
I must ask though, exactly what are you qualifications? That answer makes me think, Physics teacher?

My response was going to along the lines of, on the suction side of a pump all you need to remember is the higher you get the harder you need to suck.

And if you are sucking on a vaccuum like Monica was then you must suck really hard to get a result.

I am with Airportwo on this one. If you have a producing well, you will not get to the point you are elluding to. On our well, we have pumped over 20 gallons a minute with no draw-down on an adjacent well 2 meters away. The aquifer is a good one. If you want to draw a vacuum you need to be in solid rock with no inflow of water anywhere.

Finally answered my question in thinking through some of the replies. The pressure head is indeed the same in both cases but since it is in PSI, mathematically you can determine how much weight the larger bore is supporting. The pump suction does not care about that weight however as it starts to draw water as soon as it overcomes the pressure.

Originally Posted by ootai

I must ask though, exactly what are you qualifications? That answer makes me think, Physics teacher?

no, I am not a teacher although I have needed to teach my daughters physics, maths and chemistry when they needed help

Originally Posted by thailazer

If you want to draw a vacuum you need to be in solid rock with no inflow of water anywhere.

not a vaccuum, negative pressure, as illustrated with pinholes in the box

if your aquifer is flowing well then there will be no problem

Originally Posted by Ratchaburi

The best well system is submersible pumps, it will deliver high pressure in shallow depth well or Deliver water from 90 metres 290ft deep well at a lowwer pressure.

Unless you have a steel casing, then lightning is your big enemy.
So expensive to replace.
But, I agree it is a good option. quiet too.

^a very expensive option for a shallow well