DIY overflow not working well (pvc)

[Eric L]

Well, I build a whole sump, overflow ect today and with the pump it only cost me $100 for everything. Anyways the overflow is not working verywell at all, it does some gph but not alot.

The pump I got is rated for 600gph and the overflow alone is nowhere near keeping up. I used 1" diameter pvc, the walls are pretty thick though, maybe a factor?

At no point in the line is the diameter of the pipe reduces below 1".

I wish I could take a picture but I cant.

I am going to go from highest hole to lowest hole

The highest opening of any sort is the air hole on the external side where the pipe comes up again

The next highest is the intake on the internal side

Next highest is the 3 way piece that leads to directly to the sump to the overflow

2nd to lowest point is the bottom of the overflow on the internal side

lowest point is the Bottom of the external side.




Did I get something out of order and is that the reason its not working well?





I have an idea to fix the flow rate issue if nothing is fixably wrong with the overflow, can I just create a direct siphon into the sump from the tank that is slower than the rate of the pump but fast enough that it makes up for the short comings of the overflow?



I changed my design a little bit also though, instead of having a one way check valve at the peak of the siphon, I have a ball valve at right near the outtake into the sump. When I want to prime the siphon I just close that valve and inhale through the airhole that is on the external side where it comes out of the three way piece. This sucks in water through the intake on the outside and starts the siphon stagnant. I think this may be not get rid of alot of the air but I dont know.




Help is really appreciated because I want to set up my first SW tank tomarrow.

Thanks,

Eric

 

[rayman45]

i wish i could help...umm.. maybe put a valve to restrict the pumps flow

 

[Nic]

restricting the pump will put alot of pressure on it and will make it burn out quicker

 

[adc-aquatics]

Draw a picture with MS Paint and label it. You will be able to post that.

 

[CHOMPERS]

The pump I got is rated for 600gph and the overflow alone is nowhere near keeping up. I used 1" diameter pvc, the walls are pretty thick though, maybe a factor?

1" sch40 will not flow 600gph at ambient pressure. PVC comes in different internal sizes; sch20, sch40, & sch80. The lower the number, the lower the strength and wall size, but the larger the internal cross area. Schedule 40 is the most commonly used, except in residential irrigation. Sch20 will work well for tanks as long as it is not exposed to a high traffic area. Fittings are all sch40, sch80 fittings and pipe is gray (not conduit), sch20 fittings do not exist but sewer fittings have larger inside diameters than regular sch40.

The formula for internal area is .785x(inside diameter)x(inside diameter)
(pie are square - modified for non-math-majors)
1" ID=.785 in^2
1.5" ID=1.77 in^2
2" ID=3.14 in^2

Flow rate is determined by what restrictions you add to the system and what pressure or suction you can influence on it. Every time you add another fitting (other than straight) you are increasing the restriction on the system. Since it is a gravity system, nix your holes. A syphon only works because gravity is pulling on the external collumn of water while suction keeps it filled from the internal collumn. The longer your external collumn is (below the surface level in the tank) the faster the system will flow.

At no point in the line is the diameter of the pipe reduces below 1".

Your overflow should have six 90 degree fittings and one tee. That is seven times that the water must change course; every fitting adds restriction.

I am going to go from highest hole to lowest hole

Put tape over your holes and test run your overflow. If you do not have a dramatic improvement, scrap your design.

...When I want to prime the siphon ...

SCRAP YOUR DESIGN.
A proper overflow is self priming after it has once been filled with water. Even after a power failure, it should begin working without your help.

 

[mjime714]

I built a pvc overflow with 1" sch40. I also run a 600gph pump and it runs well at full power.

I had the same problem with my DIY overflow. I did the oddball design and had a similar problem where the flow was not strong enough. I used a coupling like this to adjust the hight of the in the section labeled "this tubes length is cut to desired water level" in the picture below:

This allowed me to adjust the flow of water more than the water level. Dont ask me why, but the shorter I made that section using that adjustable coupling, the more water flowed, but it did not effect the water level. Just the flow rate. You may need to put an extra couple inches of PVC at the siphon break so the water does not overflow.