1200gph CPR Siphon Overflow

[asudavew]

I've recently just installed a CPR overflow.

I'm having problems where the water enters the overflow.
The turbulence of the water entering the overflow is creating bubbles which then enter the siphon.

I do have a pump hooked up to the air outlet on the overflow, so I don't lose the siphon.
But if the pump goes out the air will kill my siphon.

My wife would kill me if 30 gallons of water flooded our floor.

I'm sure there is a simple solution.
So, how do I keep the bubbles out?

Thanks!

Dave

 

[asudavew]

Bump! Bump!

Help me out gals/guys!

 

[Justin1989]

Add a sort of spong type filter in the intake? worth a try. this would gather almost all of the air bubbles I would think.

 

[partypalooza5]

does the water cascade way down into the skimmer?
if it does then that may mean its not low enough in the water or theres not enough water in the system. (atleast I think.. someone correct me if im wrong)

have you tried making sure its all level too?

 

[asudavew]

I let it run all night last night.
I'm not seeing many bubbles this morning.
Maybe I just had to run it awhile?
Before last night.. I ran it for maybe 30 minutes or so Max...

 

[jsoong]

Air trapping is a problem with HOB overflow. It took me a while to figure out how mine should be set (a DIY version.)

The main setting is how high the water is over the raker teeth & also how deep the inside box is. Since you can't make the inside box any deeper, you will have to play with setting the box height. Move the whole thing up or down (just 1/8" will make a big difference) so that a continuous sheet of water flow into the box .

Failing that, you can raise the wier in the back box (that divider that controls the water depth in the overflow) by gluing on a piece of plastic. <I just slip on the back plastic piece from the glass top, the channel fit snug enough to control water depth.> With more water depth in the overflow, the water has less distance to fall into the outter box so there is less turbulance. Also, more depth means more time for air to rise before being sucked into the siphon. Also, the higher depth makes the overflow quieter. <PS. I don't think putting a sponge in front of the siphon is a good idea ... if that gets bloicked - and it will - you will flood.>

I think you are seeing a difference overnight because your water level had changed (maybe a bit of evaporation had drop the level?), or perhaps your prefilter in your pump is clogged a bit so the pump flow is less .... <Happens in my setup weekly .... a clean filter gives good pump flow & everything is set up right. Over the week, stuff collects in the pump prefilter & my system gets louder as the pump slows ..... an enforced cleaning reminder!>

Finally, you need to maintain that venturi pump on the wier type HOB OF. The flow is slow enought that air-trapping is a constant threat. <I switched over to a single siphon tube, and the flow is fast enough that any small bubbles get flushed out.> Also, you should raise your return pump in the sump so that it will run dry if the siphon fails (so you won't have 30 gal of water on the floor!) <Another option is a float switch to kill the pump, but I like to make it physically impossible for my OF to flood.>

 

[asudavew]

Wow! Thanks for taking the time to write all of that.
I will give it a try.

I will move the pump higher this weekend. Good idea! I should have thought of that!

 

[Ziggy953]

Hmmm....Your issue could be much more simple then it seems. Couple things though. Which tank is this on? You have several listed in your "my tanks" info. What size return pump are you using and give me a quick run down of the return plumbing and the drain plumbing coming off the overflow.

I have a 120g tank with dual 1200gph overflows and they are running at about 900gph each. Your problem could be the amount of return from your pump and not an issue with your overflow.

 

[asudavew]

Well the overflow is on the 110 gallon.
I finally got it up, gravel in, and filled it.

I have the overflow plumbed with two 1"1/2 pvc pipes.
they go straight down for about 24 inches, then a 90 elbow, a one foot run, and another 90 then another foot.
*OVER FLOW*
|
|
|____
......|
......|
***********
5 GAL BUCKET
RUBBERMAID

The water empties into a 5 gallon bucket that has media inside and holes drilled to allow the water to escape.
From there it drains into a 36 gallon rubbermaid container.
I built a structure out of 2x4's that the container sits in, so it is well supported.

As for the return pump.. I got it used when I bought the tank.. so I couldn't find information on it....
I will pull it out and see if I can find any info on the pump again tonight.
I looked at it, but maybe I missed something.

The pump has a 1" pvc return line. Two 90 degree elbows up to the tank and two 90 degree elbows over the tank.

The distance from the pump to the top of the tank is about 5'6.

*tank* _
|*|
...|
...|
...|____________
.......................|
.......................|
.......................|
................**********
..................rubbermaid
................**********
....................PUMP

I guess I could hold a 1 gallon bucket on the return and see how long it takes to fill up and compute the gph for the return and then do the same thing for the overflow...
I had not thought about that.

So if my pump is too slow for the overflow.. that could cause the bubbles?
I have a 700gph pump I could add if needed.
It's brand new and sitting in the package... (actually i have two 700 gallon and two 500 gallon) (sweet clearance deal at Petsmart)

Thanks for your help.

 

[jsoong]

Slow flow won't cause bubbles in the siphon, but it will not flush the bubbles through, so they collects.

I used to have 2 siphons in my OF (thinking redundancy), but with my pump (at 750 gph), the flow is too slow & the small bubbles collects in the siphon tube. Removing one increased the flow in the siphon & any bubbles just get flushed out the other side.

 

[gzeiger]

There are several simple ways to lower the turbulence of the overflow that might be easier things to try first. Instead of a sponge around the siphon tube, a ring of sponge around the outer edge of the overflow box would slow the falling water as it approaches the water level and prevent it from splashing. Alternately a ripped up pot scrubber or similar could provide more surface area to allow laminar flow without splashing.