IMO your air filter is way too small for that high volume compressor (3/4hp, 10cfm). That air pump is moving about 106,000 gallons of air per 24 hrs. There is quite a bit of dust and dirt in every million gallons of air. The small filter you have on that pump will plug up pretty fast depending on the air quality going through it. Check that existing filter at least twice a year for free air flow. A clogged filter reduces efficiency of the 'pump', thus diffusers are less efficient and move less water.
Pressure relief valve setting can vary depending on how deep the pond is and the type of compressor. As a general rule for a rotary vane, Gast Mfg sugggests relief valve setting to be at 15psi. Adjustable pressure relief valves usually start 'weaping' air at about 2-4 psi before full air release; depending on several factors.
It would have been easier and quicker to put a 3/8" close nipple & bell reducer (3/8"x1/2") on the pump instead of retapping the head of pump. Both will be just about as efficient for air flow for that short distance. You will see a more efficiency air loss when that air filter begins to clog compared to enlarging the outlet pore of the compressor.
Last edited by Bill Cody; 01/17/11 05:29 PM.
