Water well 500 feet, solar pump, BUT what kind of pipes???

[ert345]

Hi,

I have a water well 500 feet deep and i am going to install a 1KW PV system with DEGER's Top-tracker and the Lorentz HR-04H with the PS-1200 controller to lift 8m3 (about 2100 USgallons) per day. This system i guess it works, though only in theory.

The problem i have is the pipe to transfer the water from the pump to the surface.

the pump makes about 4 BAR pressure (58 PSI) and a water column of 150m high makes 15BAR pressure. the pipe is already submerged in water of exactly the same depth i.e.

the pipe is enclosed in a pressure of 15BAR (217PSI) at the bottom.

What kind of pipe to use?

in my country plastic pipes can withstand up to 12BAR(174PSI) but some people insist on using it. the alternative would be iron-galvanised pipes which cost a lot and weigh a ton!!! i want to avoid them if possible.

anybody with similar experience?? any advice???

[GaryGary]

Hi,

You might take a look here:

http://www.endot.com/support/technical_pipeselect.asp

It pretty much verifies your thinking.

I suppose one option would be use a higher pressure pipe for the bottom part, and 200 psi poly for the rest.  It looks like 200 psi poly would be good for the top 350 ft.

All that said, the poly pipe is designed for high margins -- I believe that actual burst strength is about 6 times the rated pressure, and the pipe will probably be cool, which helps is pressure allowable.  If it were me, I'd be tempted to try the highest rated poly I could find.

My 240 ft well uses rigid PVC with screw couplings.  Not sure what its rated for.

The Endot site that this link came from is good -- I would have a look through their tech library and see what you find.  You could also drop them an email.

Pressure ratings for PVC and CPVC pipe:

http://www.engineeringtoolbox.com/pvc-cpvc-pipes-pressures-d_796.html

Looks like it might work -- note the high burst pressure to rated pressure ratios.

You would have to work out the coupling arrangement.

Gary

Here is a note from the Endot applications doc:

WELL PIPE INSTALLATION:

Polyethylene pipe is an ideal product for use in both deep and shallow well applications. See the Depth Setting Chart

for a guide to the depth settings that various grades of pipe can be used at. Although claims for deeper settings have

been made they exceed the design ratings for all Polyethylene pipe and the installer risks rupturing the pipe if the

pressure developed by the column of water and the pump pressure exceeds the pressure rating of the pipe. No warranty

claims for depths greater than those listed will be honored.

The actual installation includes the use of insert fittings and stainless steel clamps as previously covered. Torque

arrestors and centering devices should be used to prevent the pipe and wires from rubbing the well casing. The

installation of torque arrestors and other well hardware should be per the manufacturer instructions. If the pipe has a

submersible pump suspended on it a safety rope must be installed to assist in pulling the pump. When a long length of

pipe is pulled from a well care must be taken to prevent kinking of the pipe. The maximum bend radius of polyethylene

pipe is 18 inches. If the pipe is kinked the section must be removed since a weak point has been created at the kink.

[finnsawyer]

I'm not understanding this.  Are you talking about crushing pressure?  If so, state such.  I do not know what the standard one inch plastic well pipe used around here can withstand, but the systems use check valves to keep the pipe full of water, so one would really be looking at the burst rating for those parts that are above water.  You need to clarify.

[wpowokal]

I have read this 3 times now but being rather dense I am still confused.

Can you state the standing water level of the well, ie no pumping.

The draw down at pupped rate, ie what level does the water drop to when pumping at given rate. I suspect you will not be pumping from 500 feet.

My best ill informed preference is poly suitably rated, easy to raise and lower, any threaded pipe requires a crain etc.

allan down under

[ert345]

many thanks for your answers.

Right,

I apologise. The depth of the well is 500 feet, but the water level is 100 feet from the surface when no pumping - i guess this is quite important, sorry. Additionally, the water tank for storage is located 10 feet from surface.

Further, we can assume that the pump will be placed about 30 feet from the bottom of the well.

When pumping, water level will drop to as low as a few feet above the pump (a sensor will be installed). Since there is very little water in the well, I assume that water level will be raised to normal (ie 100 feet from surface) during the night (ie no solar power) and then during the course of the day, it will drop to where the pump is, once or twice.

I dont understand the term "crushing pressure". I am asking whether in these circumstances a 175 PSI or even a 200 PSI poly pipe is likely to burst (from any cause).

Note that the pump will be suspended from steel rope attached on surface.

The pipe can be suspended from a rope as well (somehow) - so the pipe will not hold any weight.

I hope i clarified things a bit,

thanks again,

andreas

[DamonHD]

I know nothing, but asked on your behalf at a major buildings/FM show I was at today, and even the weediest bit of poly pipe (maybe 2cm external diameter) that I pointed to the guy on the stand said should have a burst pressure of 10bar or more, ie ~400ft or 100m roughly I think, so anything at all substantial should be OK by the sounds of it.

But, I repeat, I know nothing, I just thought I'd ask on your behalf since I was passing the stand...

Rgds

Damon

[wpowokal]

Andreas it is a little hard since you are unsure of the yield (quantity of water you well will give you), however from the information you have.

Well is 152 m (500') deep.

Standing water level is 30m (100').

Here in Australia blue line poly is rated for 120m head, I prefer and use poly for small submersable pumps.

So 120m is 400 feet in round figures, so with your day tank 3m (10') above ground if you used poly of this rating you could saftley set your pump at 117 m. So this gives you 87 m of water over the pump, so lets say you set your probes to pump 80M of water leaving the pump with 7m of submergance, a good safety margin.

When I set small pumps ( 4" subies) at depth I prefer to use two stainless steel safety cables, I use a stainless steel female union above the pump that has had two oposing lugs welded on, to this the safety cables are attached.

I asume your well is a minimum of 4" (100mm) so

for 80m so 3.14X 0.1x 80 = 25 m cubed of water, per cycle of bore. Now thats a lot of water.

Now crushing is not going to happen, for there to be a crushing force on the rising pipe it would have to be empty with the well full, this does not happen. Crushing force could be a concideration for the well liner but I must assume it has been professionally done therefore has adequate casing strength.

Flexable rising columbs are easy to pull up, you set up a pully ( wheel rim is good) about 1m above and to one side of the bore, them pull via the safety cable (stainless steel cable).

In sumary I would use 1 1/2 polr of suitabe rating setting the pump as described.

If you had the need to set the pump lower you could just join in a higher pressure rated poly between pump and "existing" pipe. The higher pressure is at the lower end, a poly pipe can burst if a submersable pump is run against a closed head (ie a shut valve) so best to have the outlet open and control with level probes.

A bit long winded I know but hope it makes some sence.

allan down under

[Tritium]

I think I would use a bubble pump to overcome the pipe pressure limits as it basically operates at low pressure (in the fluid pipe). Also a bubble pump has the benefit of not pumping down a low flow well faster than the aquifer can replenish it. Then I would pressurize at the surface if needed.

Thurmond

[ert345]

Thanks to everybody for their help! very much appreciated.

Thanks Damon for asking that thing.

Thanks Thurmond for mentioning the bubble pump - never heard about it.

Thanks Gary and Allan for useful comments and advice!

I have three options. The first option is to go with allan's suggestion of setting the pump at 110m from the surface of the earth i.e. exploiting 80m of water above and leaving 40m of water below unused. This is the safe option.

(unfortunately the available water will be - for a bore diameter of 25cm -:

3.14 * (0.25*0.25/4) * 80  = 3.9 m3 per bore cycle - i suspect my well can only give a couple of cycles per day)

Alternatively, i can risk bursting the poly pipe and drop the pump down to about 140m from earth surface, this will give me a water column of 5.9m3 to exploit. As Gary noted, the max PSI values for poly pipes are much higher than the rated PSI values.

The poly can always be replaced easily! and a lesson will be learned.

In either way I have thought one point which might prove crucial and correct me if i am wrong : when lowering the pump+pipe down the well for the first time, the pipe must be filled with water!

The third option is of course the galvanised iron pipes which are ... a pain. with the added disadvantage that i will need a crane everytime i need to access the pump or do anything with the well.

I have one minor suspicion though and again i might be wrong. The submerged pipe suffers from internal pressure from the water column IT contains and the pump's output flow. However, the pipe is also immersed in water at least until the static level. So there is a balancing pressure from the OUTSIDE of the pipe for as long as the level of the water in the well is high enough. I think this is what GeoM is suggesting.

That should make things a bit easier.

I will go for the poly pipe - the 200PSI as Gary suggested is not manufactured in my country but the 175PSI is available.

if it bursts then will have no other option but to use the galvanised iron pipes.

thanks again, if you have anything to add i will follow this thread.

when i am done i will post here the complete setup.

best regards,

andreas.

[Janne]

Hello!

I'd suggest not to even think about the iron piping. A few years back we replaced the old deep well pump we had. It took us 2 days to remove the old system, where an iron pipe and a conrod ran to the bottom of the well. And our well is only 120 feet deep. We had to remove the roof from the protecting building, and the raising of the pipes was also very slow.

We now have an ejector pump with plastic hoses.. very easy to raise or lower them

I'd suggest lowering the pump to the maximum rated depth of the hose. Then add another 10 meters of suction hose to the pump to maximize available water..

Btw, are you really sure that you can actually pump the well empty? At least around here (Finland) deep wells can generally be pumped as much as the pump has capacity. When we were still in farming business, I estimate the holding capacity of our well was pumped at least a couple of times during daytime, and never ran into water problems.

[fcfcfc]

Hi: Wow, I had to read this a few times... I think I have this right: From your message:

First, the max pressure the pump will do is 58PSI or .43PSI per vert foot, so, max push height from pump is 134 Feet.

Second, water is already 100 feet down from the top so with that pump you can only pump 34 more feet of water out of the well, to equal a water back pressure of 58PSI = pump max pressure.

Third, your pipe burst at 175 PSI is a total non issue since you would have to pump the water out of the well until it was 406 feet from the surface which would yield a pressure at the water line (down in the well) of 175 PSI..

SO, your problem, first is to find a pump with a higher head capability. Once you have a pump that can push 400+ feet, then you can worry about your pipe.....

[alternety]

I am in the US.  I have a similar pump at 500'  (well is 620').  I use schedule 80 PVC with threaded couplings (and always a safety cable - not nylon).  Works just fine.  The pump you are getting has a check valve in it. Check model - some do not need torque protection, some do (they are soft start).  I think everything that uses that controller dosn't need anything, but check.  May be a different situation for flex pipe.

To use ridged PVC you need to be able to lower/pull a piece, clamp it , screw/unscrew a section and repeat.  Depending on what you want to rig up, it may be harder for you than a continuous flexible hose.  Here the PVC is usually a 20' section.