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I noticed a mention of spraybars in the last APD. I have found the
making of spraybars to be a very interesting endeavor. They illustrate
the complexity of hydrodynamics...or maybe I am just easily
I have made all my spraybars out of black, semi-rigid 1/2 inch
irrigation riser pipe. The type available in most home improvement
places. There are fittings to attach the riser pipe to standard PVC
pipe for the input, but I never found any to block the far end of the
pipe as this is a non-standard application. So I use a piece of a hot
glue stick. I just soften it a bit with a torch, jam it in the
opening, and cut off the excess. Works fine.
My first spray bar I made with all the same size holes along its
length. I was surprised to find that the water came strongest out the
furthest hole, not the first holes. I guess the water rushes down the
pipe past all the holes and when it hits the end it starts to exit the
spraybar with the greatest force there. This is not what I would have
guessed. I tried making spraybars with the holes varying in size from
larger to smaller along the length to even out the flow. This worked
O.K., but the best spraybar that I came up with incorporates internal
baffles. I tried several different approaches before hitting on an
easy and effective way of doing this.
First I clamp the riser pipe in a vise and mark where I want the
holes. Then, using the point of a razor knife, I poke a tiny starter
cut on the end side of the hole. Then place a 1/4" hole punch (the
hollow type) against the cut at an angle and whack it with a hammer a
few times. The result should be a 1/4" hole in the pipe with the
"hanging chad" inside the pipe acting like a little scoop to catch the
water as it rushes by.
This design produces a very even output along the length of the pipe
with almost no back pressure.
Spraybars are fun!
Alan in Napa
Chaos, panic, & disorder - my work here is done.
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