i'm stumped

[monocus]

my drain for my tank has been working great for years(stockman);but in the last few months it hasn't been draining properly.some days(most of the time)it drains properly and i have a fall of 4" from the top of my over flow ;other days my water level is an inch above my overflow.my water level is usually 2" from the top of my tank as i use a wave box-but on the days it doesn't seem to drain,its about 1/2 " from the top.i checked my drain and it's clean with good water flow.any body know what is happening(besides full moon;though it does happen then)or how to fix the problem without adding another drain as i dont want to tear it apart(220 gal peninsula)

[MKLKT]

If the water level is rising in the top there is either a clog of some kind or the return pump is pumping faster than the drain is channeling somehow.

What are the dimensions of the plumbing and what size return pump are you running?

[monocus]

my drain is a 2" stockman and my pump is a bayside poseidon ps2 going into an oceans motion wavemaker with 1"return lines(4).my drain is clear as i just inspected it today.i have actually turned down the flow leading to my pump(ball valve)the thing is it doesn't happen all the time.maybe 2-3 times a month for a day or two

[emerald crab]

You might have bacterial build-up on your drain pipes. Under certain conditions, like carbon dosing, etc. the bacterial mat swells reducing the available section of the pipe, usual somewhere were you already have a flow restrictor.

[monocus]

drain is clean-i put my aquamedic scrub brush down last week and cleaned the lower drain as well

[reefwars]

Originally Posted by monocus

drain is clean-i put my aquamedic scrub brush down last week and cleaned the lower drain as well

just a shot in the dark but is it possible your pumps pumping out more than it should at times?? maybe somethings in its messed up