You might have missed, in my no tank scenario I would turn the pump on
with the irrigation controls. So the pump would not run except when I
actually needed water. Most irrigation controls have a pump lead that
can be used to fire a 24v contactor.

I had not considered the filter issues. The lake water is very clean
but obviously not perfect. I have the irrigation on a well now and
simply use a small sand trap before the valves. So what I save on a
tank might end up getting spent on a filter.


I did miss that. In this case a tank is not needed. Sometimes you can get
a combination of start and stop pressures that cause a pump to start and
stop repeatedly that is not the sort of thing a tank is intended to
solve. This happens when the pump can hit the stop pressure while
running. Either the pump makes too much pressure or the flow being drawn
is too low for that pump. This may happen to you because you have a low
flow low horsepower situation which may lead to an over-sized pump.

Easy solution would be to just throttle it down a bit. So make sure there
is a valve in place downstream of the pump and preferably near the pump
that you can turn down until it behaves. A globe valve will hold a
setting better and be less likely to get 're-adjusted' by someone else.
Ball valves are OK but need a wire or something to prevent them vibrating
to a different setting. Hang a note on it stating it is a throttling
valve and not to be adjusted by others.

If you are just running at 2 gpm you could try a simple screen filter
like the one frim the site below;

http://www.sprinklersupplies4less.co...ete-unit-mesh-
polyester-p-22530.html

This is the 1 inch size 250 mesh screen. I have either this unit or
something very similar on my geothermal open loop system, except in 1 1/2
inch size with 100 mesh and my filter box says BII on it. Looks the same
as the photo.

The 250 mesh is recommended for drip irrigation. Cost is shown at $70 and
replacement filters cost $36. These are tough units with clear cases so
you can see if there is sand in the bottom that can be cleared by opening
the valve for a second. You can also see if the filter is dirty. I have
been cleaning mine every 3 months or so for 4 years and am still on the
same filter. Use plumbers grease on the o-rings and threads everytime you
re-assemble the unit and it should last a long time. Grease is essential
or high forces are needed to remove the case to clean the filter and I am
sure those forces will reduce the life of the unit. Sure reduced the life
of my wrists before I twigged to the grease. Plumbers grease is best as
some other greases will deteriorate plastics or rubbers. It can take a
bit of force to turn the case into the body of the filter so make sure
the body and it's pipes are securely anchored and can tolerate heavy
twisting motions.