overflow to sump ???

[morval]

so i just spent all day sunday finishing my canopy build,moving tank and painting the wall behind it, and adding a sump. i got a overflow rated at 500gph and a mag pump that does 500gph, thing is the overflow drains a lot more than the pump returns. having seen a lot of build here i had invested in a ball valve for the drain and return. after a lot of tweaking and sleeping only an hour at a time(on the coutch next to the tank) i got it to balance. my question is since they are both rated at the same gph shouldent they just work automaticly? drain is 1" and return is .75" is that the differance? or is there that much head loss, line only rises 38" with two 90's ? hope it is doing all right while im at work...GF will be reall mad if theres a flood

 

[tlarkin]

head loss. Youre not seeing 500gph return in your tank. I would have went with 1.5x the overflow to compensate for headloss. A mag7 would have probably been easier to dial in and give you better flow at both ends.

 

[hurt]

Originally Posted by tlarkin
http:///forum/post/2710354
head loss. Youre not seeing 500gph return in your tank. I would have went with 1.5x the overflow to compensate for headloss. A mag7 would have probably been easier to dial in and give you better flow at both ends.
What Tlarkin said^^^^. You are probably seeing between 350 and 400 gph actually returned to your tank unless it's a pressure rated pump. Buy a pump that is a couple hundred GPH higher than your overflow is rated for is most always the way to go. If your overflow can't quite keep up with your return pump, you can always put a ball valve on the return line to match them exactly. Many pumps tell you how many GPH they will do at a certain head height.
The drain is gravity fed at 1 inch because water will only flow so fast with only the help of gravity. Which is why the drain line is bigger than the return. The return has force much greater than 9.8 m/s your return line has. So you can force more water through a smaller pipe in your return.

 

[morval]

thats the answer i was expecting thanx guys guess ill buy a new pump sooner or later

 

[natclanwy]

Your overflow cannot return more than the pump returns, if your pump sends 10g per hour your overflow will drain 10g per hour no matter how big the overflow is. To size a pump for an overflow you need to determine how much headloss you have by figuring how many verticle feet of plumbing you have. Elbows and valves will add additional headloss but not enough to make much difference. So if your mag5 has 5ft of verticle plumbing your flow after headloss is only about 230gph not really enough to safely maintain the siphon for a 500gph overflow. Low flow is probably the biggest cause of floods associated with HOB overflows. You should try to size your pump between about 70% and 100% after headloss is calculated of your overflows rating if you need to error on the side of slightly too much flow.