Centrifugal Pump Double Duty

The well is 4 inches in diameter and the architect tells me the well is 18 meters down. I rounded off to 20 meters in my question. They didn't mention anything about a venturi type pump below.

My basic question is not to do with the well. Its with the pump itself. It currently pulls water up somehow through an 1-1/2" pipe and pumps it into the pool through a 1-1/4" pipe.

If I install a tee and valve to redirect the water to a 3/4" diameter, 50 meter long garden hose will it cause any problems with the pump since it was installed with an 1-1/4 outlet rather than a 3/4" outlet, i.e., it will pump out to a smaller orfice in the "garden" direction.

And, by the way, thank you for your response. It was indeed helpful. Slowly I'm learning more about what water pumps can do.

You could aways tee it off with 1 1/4" line and run it back to the waste water well with your 3/4' hook up on it. Placing a valve on the line at the well to choke it off until you get the pressure you need on the garden hose.

I am not exactly sure of your real question; it seems you have two, or more, separate processes, issues or questions, a well to increase water availability, and then watering the garden.

First, most of Merida is old and of a colonial design and may have laws against wells, in some countries, even in the USA some states, own all the water rights. Second, is there even fresh water available under-ground as much of Merida is near the coast, you did not specify where I know there are outer areas even old sisal plantations. However the question then becomes multi-fold, assuming you can legally drill a well and there is a fresh water aquifer, in that dept as some pumps for wells are designed as suction, very low lift, others use jet venturie suction (low efficiency), as well as there are dedicated in ground (down the bore hole), you did not specify the diameter of the well so I am assuming that with the typical Merida homes bringing in heavy equipment to drill a well in your backyard may be a problem, depending on your location again.

Second, you did not specify any parameters of your garden such as size, crops, etc. If it is a small garden, and depending on the crop, a drip system may be much more useful as it use minimal water amounts versus the large radial sprinklers or irrigation canals. As you said "city water" I am assuming this is a small "garden" not a commercial sized operation.

I have tried to provide you with some ideas and answers but your specific needs and usage I had to make many assumptions so I may or may not have answered your needs. I am in the process of helping redesign the economy and infrastructure of a village in Indonesia, public water, maybe available 3-4 hours a day and same for electricity. However they are blessed with good water resources for farming as well as for building small micro-hydro systems. The "public water" is not potable, you may have the same situation, and all drinking water at least for me and the family I stay with, is bottled, well at least by USA standards not potable so we are also contemplating drilling a new well (or wells) a few are already there, but the water quality for human consumption is poor as they are shallow and contaminated with fertilizers to heavy soil suspensions, so we may face the same question but on a village wide scale for home use not farming where the traditional gravity flow and redirection of the river via irrigation canals works very well for farming which is literally the life blood, they grow most of their own food rice and corn, we are adding fish farms to increase protein in the diets, but we do not have a shortage of water just potable and reliable home usage.

I hope this at least helped you define your needs better as well as made you think about legal issues as well as design. A "Garden" implies it is a small area not a commercial farm. But this could be a rose garden where the plants are not replanted every season(s) or a small corn garden where it is. Therefore your crop, size, planting method, etc. will all need to be considered, you cannot plow a field if you have underground and small sprinklers as plowing, tilling, would/may destroy the pipes, is just one example.

Whew, you went way off track. In Merida, as in all of the Yucatan, you can pretty much punch a hole in the ground anywhere and hit sweet water. The deeper you go the more pure the water. In Merida, a city of nearly 1 million people, there is no waste water management to speak of. they simply use septic type systems. Any property owner wishing to get more water than the city can provide can drill a well and pump up water. Every pump I've have seen is of the centrifugal type, generally bringing water up via a 4 inch pipe. Depending on the function, the shallower , 10 meter well is used for waste, and the deeper, 18-20 meter well is used to bring up good water. If one desires to go deeper than larger equipment is brought in and an 8 inch hole is drilled down to 30 meters or more. I don't condone the way they do it here, but that is how its done. Its not illegal.

My question is really only about the pump being used to draw water up to fill my pool. I wish to install a tee and valve and redirect the water into a 3/4" garden hose, 50 meters long, to water the plants and grass around my property. If I do this will it cause any problems with the pump, as it currently has an 1-1/4 outlet and I'm going to tee off and shut the 1-1/4" pipe, and redirect to the 3/4" garden hose, then switch back to the 1-1/4 as may be needed for topping off and filling the pool.

I suspect I'll just get more pressure, but since I don't have much knowledge of what goes on inside a centrifugal pump I don't know if more pressure will cause some problem with the pump I may not be aware of. I would guess the electric motor will experience more load, and therfore more heat. but ??? And the pump itself ???

I can always buy another pump and draw water from the pool, but since the main pump is mostly just there doing nothing I thought I might be able to get more use out of it. By the way the pool does not use clorine to kill bacteria. It uses copper ionization at .5 parts / million. Drawing water from the pool is an option, but I would rather not disturb the volume of water as the alkalinity of the well water is quite high and I'm always battling down the the numbers.

Thank you for your response, and actually your reply was quite interesting.

After my long disertaion, the simple answer if the volumne of water is adequate then a Tee and a valve may solve your problem.

This will give yo the basics of well pumps;

http://www.watersystemscouncil.org/vaiwebdocs/wscdocs/2567958wsc_inst_20.pdf

As far as the double duty; when you reduce the discharge of the pump, depending on the design, it may just boost the pressure not the volume. The Volume is the constant in the pump information you gave, but it is based on a certain lift and inlet/outlet sizes. If you are only getting a 'trickle' out of it, I would calculate the ft of head, lift and line losses. If all that is within the design of the pump specs tehn I would be inclined to believe the pump need repair/replacement.

Here is some more info;

http://www.popularmechanics.com/home_journal/how_your_house_works/1275136.html?page=3

and

http://www.irrigationtutorials.com/pump.htm

~ T.R. North ~ Maxozone@comcast.net

I think you just answered my question. If the discharge (water exiting the pump) is channeled through a smaller opening I'll get more pressure (but not more volume).

That ok. you are telling I won't hurt the pump. The "trickle" part is not about the pump. Its about the city water coming into my property, i.e., its quite low, and not very useful for watering plants and grass around a house.

My pump as it is now is fine.

Thank you for your response. If my understanding is the same as what you were saying then I've learned something today. Thanks again. And thanks for the useful links.

Why not install a cheap pressure gauge in the pump discharge if there is not one already. Open the valve you have constructed to allow watering of your lawn. Slowly close the pool fill line while watching the pressure gauge. If the pressure rises above the rated pressure for the pump or piping being used, you will need to use additional pumped water volume in some way. Either into the pool, or an additional water discharge for the lawn. Perhaps into a storage tank or drum for future use. Be ceative. Good luck.