Connecting Wellpoints to Pump

In a previous post, I wrote about collecting rain water for flushing the toilet, and making three wellpoint holes.  Now I had three pipes coming out of the ground, and needed to connect them to the pump.

I wanted to use the same pump to irrigate the garden, so needed a tap which could feed water from the tank to the input of the pump, and also a manifold to be able to direct the output of the pump into one of several irrigation loops, or into the tank.  It was surprisingly complex!

A combination of clear pipe, taps and connectors allowed each of the three holes to be turned on or off independently.  The clear pipe sections show if air bubbles are being drawn up from each hole, and also how muddy or clear the water is.  Most importantly, it allows the source of any air leaks to be isolated. I rigged it like this partly because of what I had seen next door where the neighbour has a wellpoint installed professionally. That system did not use a tank, but fed directly from the pump into the irrigation system. There are five collection points under the ground, and one or more of them pumps up air, which results in a very irritating hissing and spluttering noise when its in use. Since all five points are permanently connected using opaque black piping, without any taps, its not possible to know which point or points is sucking up air.

There is a fourth connection point in the photo, which could be used for another wellpoint hole in the future. For now, I use it to empty out an unused pond when needed.

Its really important to get all the connections airtight, otherwise bubbles of air get sucked into the pump, which can accumulate and make it stop pumping.

The green inserts inside some of the clear tubing were needed because a length of it would get sucked flat when the pump was operating, restricting or even blocking the flow of water.  I designed one for 15mm tubing and one for 20mm tubing, and printed a few of each using green ABS (acrylonitrile butadiene styrene). Dipping them in acetone and hanging them to dry made them much stronger and also smoother.  They are a snug fit when pushed into the tubing, and prevent it collapsing while allowing the water or air inside to be seen through the oval holes.

Next was a pump.  I had experimented in the past with bubble pumps, where an air pump on the surface pushes air down into a narrow pipe lowered into the ground water.  It didn’t work too well – perhaps I will write about that sometime.  I had decided against submersible pumps, as it is nerve wracking lowering an expensive pipe down a hole!  So I wanted a self priming surface pump.  The neighbour used a 750 watt pump, which was the same one recommended by every hardware and plumbing shop I went to.  I wanted something a bit smaller, because I didn’t think that there would be enough flow to warrant a 750 watt pump.  Eventually I found a 370 watt pump, but the listed retail outlet for that brand insisted no such pump existed.  Eventually the wholesaler agreed to sell me one directly.

I also bought a filter, and a brass 20mm non-return valve.  The non-return valve prevents water flowing out of the pump, which means there is always a bit of water for the pump to “bite” on.  The pump recycles water, which means it can pump air out of the pipes when needed.  Initially I put the non-return valve before the filter, which was a mistake.  When sand was drawn up with the water from the ground, it would sometimes prevent the non-return valve from sealing.  That resulted in the pump and pipes slowly emptying, and then it could no longer start up without being physically primed (i.e. by pouring water into it from above).  After cleaning the valve out a few times, I swapped them around to filter the water before the non-return valve, so that it no longer got clogged with sand.

Its really important to use lots of plumbers tape, or silicone, or both, to ensure all joints are sealed. When the pump is running it generates a lot of suction, which will draw in a stream of air bubbles from the smallest of leaks.  I used tape for the metal on metal connections, and silicone for the rest, allowing it to dry overnight. When I redid the connections, I arranged it so that the filter housing was level, which had two advantages. Firstly, it allowed water to flow out of the housing which made it easy to flush out any sand that settles there.  Secondly, I could put a foot on it to brace it in place when I removed or tightened the filter cap, so that the silicone seal would stay intact.

I found that the 2.5 meter hole was a bit too shallow, and if its tap is opened wide, after a 20 seconds or so only a stream of air bubbles comes up it, which stops the pump working well.  however, for a day or so after a good rain, it can be opened wide which results in a much better rate of flow into the tank.

The final step was to saw the side off a a plug point to fir it into the pool pump electricity box. An inline timer allowed the pump to be set to switch on for 15 minutes six times a day.  That is enough to fill the tank, and allows the water table to recharge in between pumping.
This allowed water to be pumped into the tank, but what about using the pump to direct water into the various irrigation circuits already in place?  All that was needed was some sort of manifold – how hard could it be?