spray bar

[Dan Dixon <dandixon at mac_com>]

> Hi list members, I don't post often.I read the list every day and have
> learned a lot from this list. Now I would like to add a spray bar to my
> planted tank. I have a125 gal tank with a 20 gal sump powered by a Mag
> driven 250 gal per hour pump. The piping is 11/4 in.  I think that I want
> the bar to be 5 ft. it will fit between the return and the overflow at the
> other end of the tank. The return is about 5 in below the water line. What I
> need to know is should I make the holes in the spray bar different sizes or
> all the size?  I will have to decide what size holes that I will need. Are
> there any formulas for this? Thanks for any help.
> Blendia

You can make them all the same size. Hydraulic pressure will force more or
less the same volume through all the holes. Same way a garden sprinkler hose
works. With air it's a different matter, since air is more compressible, but
water behaves hydraulically.

I don't know of any hole size formulas, but basically you'll want to make
the total hole size of your spray bar (area of all the holes added together)
at least the size of your return pipe's opening area. Assuming a return pipe
diameter of 11/4ths inches:

1.25/2 = 0.625 (radius of pipe)
0.625 squared = 0.390625
0.390625 x pi (3.1415) = 1.227148437 square inches

If you drill one hole every 6 inches (10 holes total) you need holes with an
area of at least 0.1227148437 square inches each. Reversing the circle area
formula we get a hole radius of 0.1976423537, or a diameter of about 0.4 of
an inch. Use a 7/16 inch drill bit.

If you drill one hole every 3 inches (4 per foot, 20 total) you need holes
with a diameter of about 0.14 inch each, or about a 3/16 inch drill bit.
Etc, etc.

Just always err on the high side (round up) and you won't restrict your
pump.

Dan Dixon
PS.  Someone be sure to check my math!!! :)