diy overflows
if you have a tank which is drilled to accomadate a sump system then you have no need for this however if your tank is not drilled and you don't want to drill it then here are an idea for an overflow that can hang on the back of your aquarium.
pvc overflows
as the name says this overflow is made from pvc piping and can be built in a minimal anount of time. basically just follow the design in the pic and your done.
note
- the tee that goes to the sump is located above the internal u this is important to syphoning action
- the black cylinder on the top of the unit is an air check valve this makes drawing the air from the system much easier
- the height of the intake is cut to match the height of your water level
- if you find the overflow to noisy you can cap the vent but make sure to drill a hole into the cap to allow enough air in to keep the syphon going.
how big should my pipe be
the diameter of the pipe depends on the amout of flow you want through your system. ex. if your tank is 100 gals and you want a 4x low rate you would need a pipe large enough to accomadate a flow rate of about 400 gals per hour. also you would need a pump capable of pumping the same 400 gph to return the water to your tank.
below is a chart that give the gravity flow rates of various size piping
pipe size flow rates
3/4" 330 gph
1" 600 gph
1 1/4" 910 gph
1 1/2" 1300 gph
1 3/4" 1800 gph
2" 2350 gph
2 1/4" 2960 gph
2 1/2" 3650 gph
2 3/4" 4450 gph
3" 5280 gph
this overflow design works flawlessly i have built one and an now using it for my sump filter and i've tested it to check if it loses it shyphon in a power outage and when i restored power to the pump it started up again 100% of the time.
the total cost for this ran me about $25 cdn.