Hello all

one of our products maintains a water level of 1/2" when not in use. Looking at adding a slow type of drain hole(about 1/8" dia) in aluminum that will always be "peeing" while in use but will allow the remaining water to drain when not. Wondering if anyone has any knowledge of hole shape/size/dia data so this low head height water will drain without just covering over the hole due to surface tension of the water. Maybe the hole should be tapered? maybe a radius on the top edge? Trying to get a feel for any applications out there before testing....

Maybe an off the shelf small NPT "muffler" like used on a vacuum pump or air tools, would have the desired effect of wicking out stagnant water, but also reducing "active" leakage better than an open hole. Will only work if it drips, meaning you might need to tie a string to it.

Small holes tend to plug with debris easily. What is the problem with a larger hole?

a larger hole would cause loss of pressure in the chamber in question during use.

a micron filter we use upstream should negate this some but its still a concern..I agree.

Our options here are limited.

Sounds like you need a drain line with a float valve.

Sounds like a toilet to me??

Thanks everyone

I'll have to ponder the drain line with a float...

Am testing different shapes of small drain holes this week.

Try a plug-resistant orifice, such as those supplied by CU Services. Follow the link below:
http://www.cuservices.net/index2.html

I think MiketheEngineer may have been suggesting a P-trap, like you find under a sink. These are commonly used in condensate drain lines of A/C units. It allows water to drain freely but blocks any vapor flow as long as the pressure is greater than the liquid column height.