Thoughts on low-tech water pumping

[Ernest T. Bass]

Ramble alert! I may start talking to myself here... Feel free to join in the conversation!

As we are striving to be as self-sufficient as possible, we have always been aware of the need for a reliable off-grid water system. Problem is, the budget's extremely tight and we would like to try and stay as low-tech as possible, to keep maintenance and repairs feasible in the possible times to come. This rules out your typical solar or wind generator battery bank system..

We have always thought that a mechanical water-pumping windmill might be the way to go, as we always have a nice breeze with our 1/2 mile pasture behind us and only a few miles to lake Superior. We actually almost got our hands on a used one not too long ago.. Problem is, we would need a sizable cistern to meet the water demands of our homestead, ideally in the form of a water tower to eliminate the need for an electric pump to get the water to the house. With the winters we have here, I can't see keeping a system like that from freezing..

The Airlift windmills have perked my interest, and I wonder if would be at all possible to build one from scratch? Maybe make a compressor from an old lawn mower engine? All you need then is a couple pipes going down into the well, provided that the static water level is high enough from the bottom. Our well is something like 125 feet deep, but I don't know the water level or how to check it. Wells give me the creeps, so I like to avoid them... Nevertheless, water is a necessity..

Now, I thought I read somewhere that since the airlift pump delivers water with such a high amount of oxygen that you can actually pressurize a large airtight cistern. Would this be possible, or am I crazy? If the cistern could go underground, and the windmill could pressurize the water, and the windmill could be made from scrap, I'd never ask for anything else in my life...

Any thoughts on this?

Thanks,
Andrew

[glenn kangiser]

Lets start with the well first, Andrew. 

A well if properly maintained and sealed is one of the cleanest sources f water you can get - provided there are no polution plumes etc around.

Diameter?   Things you see on the well head?   Possibly an inspection plug - usually 1/2 or 3/4 pipe?

Not the same hole the pump comes out of.  Being in freezing area you may have something different than we use here in the West.  Possibly a pit or pitless adapter that sends the pipe underground under the frost level?

[Ernest T. Bass]

We have a surface jet pump at the moment. There may be an inspection plug now that you mention it... Diameter is probably 6''.

[glenn kangiser]

Not underground etc to keep it from freezing?

If there is a plug, you can take a clean stick and a string and lower it into the well until you hear or see it splash - mark the string then pull it out and measure it for static level.  If you don't hear the splash measure the dry string until you get to the wet part.  That or a bit lower is where you have to concern yourself with pumping from. 

Your well driller may have a report with the static water level and bottom depth etc. on it also.

[Ernest T. Bass]

The pump is in a small insulated lightbulb-heated house. We didn't have the well drilled... Is there any concern of the string getting caught on something and breaking down there?

[glenn kangiser]

Slight possibility but not likely - use a clean stick and string and it won't hurt anything if you lose it anyway.  Maybe drill a hole in the end to secure the string so it hangs straight down.  I have used wrenches also if going to feel the bottom - Oh - yes --- clean of course...

[Ernest T. Bass]

Thanks for the tips; we will definitely need to do that if we decide to try and move forward with a plan...

So, have you ever heard of basically a giant bladder tank of sorts? Would even be possible?

[glenn kangiser]

Actually for small amounts it could be feasable, using just bladder tanks although rather expensive.  Airlift is fairly inefficient and anything you tried to pressurize with it would serve to stop it from working.  I think I would just go with a positive displacement type wind mill pump or if you were set on using air, let it flow free at the top into an open tank - swimming pool - EPDM pond - ferrocrete pond or underground tank - etc then a small pump from the reservior.  Remember that as things get bigger and bigger, forces on them get greater and greater.

Not saying it isn't possible - just harder to do.  I have a couple tanks - 10000 and 4000 gallons I got for removing them from the city.  Both pressure vessels - my point being that you may find something suitable for free.

[glenn kangiser]

If air is added as in a retained air rather than bladder system then a float valve needs to be added with an excess ait release to drain off the air.  An airlift wouldn't work into a pressure vessle though.

If you have ever seen a bubbler air lift pump n an aquarium for fish you have seen how an air lift works.  It lightens the water by mixing it with air so that the water with no air and atmospheric pressure on top of it pushes the air lightened water out the top of the eductor going back into the tank or in your case into a collection vessle.  A pressure vessle would counteract the atmospheric pressure stoping pumping - the air would go out backward into the well rather than bringing water up the eductor pipe.

[Ernest T. Bass]

Yeah, I guess I wasn't considering those physics... The other reasons I'm attracted to the airlift system is the lower maintenance (especially down the well), and the fact that the windmill doesn't have to sit directly over the well, as ours is in a very inconvenient location..

So, in cold climates what did people do with the water from their windmills in the old days? I doubt that every homestead had a cistern upstairs..

The water could always be pumped out of the cistern by hand, but the amount of water we'd have to haul would be ridiculous..

[NM_Shooter]

Are you wanting to use air pressure to deliver water to the entire house, or just to get it to the large cistern?

Be careful with pressurizing large vessels....

You might want to consider using a two stage system.  Put a cistern in the ground as bulk storage, then a smaller tank in a protected area, up higher, that won't freeze.  Or just a smaller tank anywhere to use as a pressure vessel.

Here's why:

The pressure that a column of water creates is .445psi per foot of lift for salt water, a little less for fresh.  Figure 1/2psi per foot for rule of thumb.  If you have a cistern that is 8' deep, and say your highest water outlet (shower?) is 8' above ground level, that is a total lift of 16 feet just to make the water weep out the head.  Add 20psi onto that just to get a usable water stream.  So you are at 28psi.

Take each square foot of space of your pressure vessel and figure out the force being exerted outward.  Heck, each 1' square has 2 tons of force pushing on it.

I'm building a windmill airpump for my fishing pond, using an old oil-less air compressor.

http://countryplans.com/smf/index.php?topic=5383.0

[Ernest T. Bass]

Okay, scratch the compressed cistern idea.. If I wanted to pump up to a water tower with an airlift system, the air injection pipe would have to go that much further below the surface of the water, correct? That would be impossible, but do you guys have any idea how the "positive pressure pump" that these airlift windmills use work? http://www.airliftech.com/ They use this pump when you can't meet the submergence ratio.

[glenn kangiser]

The air lift just injects air a little bit from the bottom of the eductor.  I don't yet know what the positive displacement pump is - maybe a diaphragm type - I see it gets pretty large in the bigger models.

[glenn kangiser]

I don't think this is a patent of that company but it explains and illustrates the technology I was describing along with others.

http://www.google.com/patents?id=RI42AAAAEBAJ&pg=PA3&dq=AIRLIFT+Technologies&source=gbs_selected_pages&cad=1_1#PPA1,M1

[NM_Shooter]

What a cool idea.  Note that the air also vents up the pipe with the water, so you would need to bleed off the air at the surface.  I think this is more of a way to bring water to the surface rather than provide pressurized water at the surface. 

-f-