Water pump

[Chas]

I am having a devil of a time figuring out what size pump to buy for a very specific purpose.

I want to pump water from a canal about seven meters away from the pump to my back garden which is about five meters further along. This is all horizontal as the canal and my garden are less than a meter different in height.

I plan to just turn it on and off as I need it. .no float or tank involved. .just simple irrigation. ( Which I need to get organized before the dry season)

I walk into Home pro and they have a whole aisle of pumps and I just do not have a clue which one to buy. The clerks are not a help as this is something I cant begin to explain in Thai and the booklets. . .even in English . .are not of any help either.

Any experts out there. .anyone with a similar installation?

I would be grateful for any help.
Thanks

[hhfarang]

I'm no pump expert, but I use 6 at my house of 3 different types for different purposes. One thing to consider is what volume of water you want to transfer in what amount of time.

If the volume is small, you're not in too much of a hurry, and if you are going to only do in infrequently and monitor it when you do as in turn it on and off, a cheap small submersible pump would work with one of those clear plastic hoses 12 meters long to transfer the water. I use this in one application with a 1600 baht submersible pump and a two inch diameter clear plastic hose that's about the length you are describing. If that (2") is enough volume for you I think this may work. It wouldn't even require any permanent pipe installation.

The only thing I'm not sure of is if you would need some sort of filter over the intake of the submersible pump to keep the canal silt from fouling the pump.

[Nereus]

Basically, to spec a pump for any application, you need to work backwards from what you want the end result to be. How many sprinklers and their output in litres or gallons per minute. How much pressure they require to flow the rated amout of water. The distance that the water has to be pumped, both on the suction side and the discharge side. From what you have written the suction should not be a problem regarding the length or "lift". It will need a foot valve and a screen of some type on the end of the suction pipe. The pump should also be of the "self-priming" type so the you don1t have the hassle of trying to prime it each time you want to use it.

It may all sound like a lot of messing about for a simple system, but if you do not take everything into account you will end up wasting money, with something that will not work, or is way to big for the job.

[PeteC]

From another viewpoint, I would do a lot of thinking about the canal in general. Will it also dry up or drop in level during the dry season? Is there now any chemicals or sewage in there that will get pumped onto your garden? What's it's source? Is it possible for sea water to flow in during the dry season? What factories or commercial establishments are alongside it's route? Pete

[Chas]

I really do appreciate all the input here guys.

The canal is fresh water and doesnt dry up and in fact our house water comes from it up the line. I believe the main source is some larger government canal . . .I could just hook up to our house system but that costs and I dont want to pay for it.

It is the figuring out of all the tech stuff Nereus that gives me the trouble. I was never good at math word problems and just reading your post is giving me a blinding headache. Self- priming yes. Thanks for the reminder of that. Very important. But I have no clue as to number of sprinklers etc. . and I dont really need a lot of pressure at the delivery end, just that the water makes it from the canal to the garden area.

I do have a filter at the intake end. I have already run a plastic pipe to where I want the pump so a submersible wont do at this time. But I hadnt thought of using a clear plastic hose for the next bit. Thanks HHfarang for that suggestion.

[hhfarang]

That clear plastic hose will probably only work with a low pressure pump. Anything with any strong pressure may require pvc piping or some stronger type of hose material (like the water trucks use).

I have a half horsepower submersible that runs 24/7 through 2" clear plastic tubing for a Koi pond and it works very well. Never had any problems with the clear plastic. It's connected at either end with simple hose clamps available at any Thai hardware store.

[komfortablynumb]

For a bunch of 'well i am no expert, BUT'!
Thanks for the sound advice.
Much food for thought.
I'll have get out my slide rule & Theodolite and not forgetting my trusty, now rusty chain.
I have 2. 1500 litre rain water tanks above ground. (at the moment)
My wonderful. And i mean that.Thai builder decided gravity would provide a good flow.
Unfortunately a bit slow.
Like an ant with an enlarged prostate.
So a pump is obviously needed to supply water for both the garden and my allotment sized small holding.
Working on the theory of watering twice a day with normal UK tap pressure.
Finaly the question.
Any one know anything about photoelectric pumps?
They are available in the UK i am not sure about HH.
I will be looking into it.
But anyone have any advice.
Thanks guys.

[Chas]

First of all, thanks for all the input on this thread! It all helped and it is so great to have a forum like this where such questions can be asked. .and answered.

OK. I bought a pump at Homepro. "Lucky Star" brand 7 year warranty. Midsize. . .one of those schoolbus yellow jobbies that you see everywhere.

Connected it to the canal pipe for inflow and then to my garden hose for outflow. ( I had it mostly right myself but needed a technician to come in and tell me I forgot a stop valve on the intake end of things!)

The whole system is only a foot or two from the ground and the lift from the canal about two feet.

It works like a charm I am happy to say but I have what may be a silly question. Obviously it comes on when I open the hose nozzle and then shuts off when I close it. But sometimes I reduce the flow from the hose down to a trickle and even when I have the hose nozzle open full, it goes on and off every five to ten seconds. ( Be patient. . . I AM getting to my question!)

Does reducing the outflow stream and/ or using a hose with a spray nozzle as the only outflow somehow damage the pump? Does it create pressures that could eventually blow it out?

I know many houses use these to pump to a storage tank but with a tank, the pump outflow is wide open until the tank is full.

[PeteC]

No, and I got that answer from a technician when I asked the same thing a few years ago. Our main house pump does the same thing when we only turn on the tap lightly, like when shaving or brushing teeth.

I have a second set up similar to yours except bore>tank>garden pushed by a Mitsubishi pump from tank to garden. When using just a small sprinkler rather than the whole system, the pump does the same thing.

There's some kind of regulator in these things where it won't suck more from the source than it needs to push out, therefore the motor cycling on and off. Pete

[Nereus]

No, and I got that answer from a technician when I asked the same thing a few years ago. Our main house pump does the same thing when we only turn on the tap lightly, like when shaving or brushing teeth.
I have a second set up similar to yours except bore>tank>garden pushed by a Mitsubishi pump from tank to garden. When using just a small sprinkler rather than the whole system, the pump does the same thing.
There's some kind of regulator in these things where it won't suck more from the source than it needs to push out, therefore the motor cycling on and off. Pete

Well, who ever told you that is not correct Pete. The running of the pump is controlled by a pressure switch, and does not really have any relationship to the flow of water. If you restict the flow the pressure will rise rapidly. Any electric motor draws anything up to 7 or 8 times it`s running amps / normal current draw. Current flow produces heat in direct proportion to the amount flowing (amps). The pump in question is "short cycling", and the longer it is allowed to do that the hotter it will get, and eventually burn out. It is also consuming unnecessary amounts of power.

If you have a situation where you continually have this occurring the best way around it is to have a "bypass" valve on the discharge side of the pump and allow some water to return to the suction, or water source.

This goes back to the original question and my reply, that you need to know how much water, both flow and pressure, that you are going to use, (sprinklers or whatever), before you can specify a suitable pump.

and Happy New Year

[PeteC]

Well, it was the man who sells pumps. Perhaps a strategy to sell even more pumps? LOL. Happy New Year! Pete

[Chas]

The technician did mention that I should put a stop valve on the outflow end, but since the standpipe is about two feet higher than the pump, there is a lot of water in the pipe that stays there when the pump is off. I dont see the point of an outflow stop valve.

Nereus, the pump does not seem to overheat at all. I have felt it after using it for a half hour or so and all parts of it seem to have stayed cool.

Also, what does the pressure switch relate to if not to the water pressure either intake or outflow? (You seem to know an lot about these things!!)

I didnt mention that the pump is called ( I have the booklet out now which I didnt before) an "Electric Well Pump" ( LSW111EA. . whatever that means) and there is a diagram along with it that shows the feedback that you describe. But if the inflow pipe has a stop valve to keep the water IN the pipe, it wont go back to the canal, it will just go into the pump again. . with some force I would imagine. .when I restrict the flow in some way. Wont water pressure IN be just as damaging? (It would be like connecting intake and outflow together like a closed system!)

PRSCT. ..how long have you had your garden pump anyway?

Maybe there are different kinds of pumps here? Mine has something called an "Air Charger Assembly" that I had to screw on. The pumps I looked at around here ( three or four houses) dont have anything resembling this "air charger" Nereus. . would this make a difference?

[PeteC]

Here at the new house only 1 year. At the rented place in Pattaya before both pumps (house and deep well) were replace by the owner in early 2007 after what she said was 6 years from new. Both were Hitachi and they started to lose pressure, and both cycled on and off depending upon useage. Both the city water and the bore water was very alkaline there which could have been a contributing factor perhaps. Pete

[PeteC]

PS: To clarify so no confusion, when I say cycle on and off, I don't mean a 2 second 'click-click'. It runs for 10-12 seconds and then pauses for the same if the output is not strong. Pete

[Chas]

Prsct, that is what I am talking about too. Five to fifteen seconds on then the same off.

I wonder if all houses are plumbed with the "return pipe" described by Nereus?