[QUOTE][i]<a href=showthread.php?s=&postid=11551407#post11551407 target=_blank>Originally posted</a> by asm481 [/i]
[B]With out a vent this set up will "wait" to flow until a true siphon starts. Then when it did form siphon it sucks air in and breaks siphon keeping level at and above the drain holes. With a vent the drain starts sooner and stays consistent. He has had this running without an overflow therefore the pump might not be to to strong. I do agree though lower flow would make a quieter set up either way. [/B][/QUOTE]

I agree. But I do have a pair of 2" dursos on my big tank that will will still syphon in spite of the vents if I try to push too much flow through them. I dial back my return pump just enough to avoid syphoning.

so will increasing the size of the 3/4 pvc to 1" do me any good? or just cut the pump a bit??

[QUOTE][i]<a href=showthread.php?s=&postid=11551483#post11551483 target=_blank>Originally posted</a> by hyrumbradshaw [/i]
[B]so will increasing the size of the 3/4 pvc to 1" do me any good? or just cut the pump a bit?? [/B][/QUOTE]
With a 3/4 inch bulkhead increasing to 1 inch will do more to prevent clogging then to increase flow very much. That said, I would go to 1" pvc.

ok, i guess my biggest concern at this point is that it maintains a pretty constant level just too high, so how would i lower the overall water level??

With any overflow, either a pvc drilled or a reef ready type, the water will find a level over the last obstruction before it drains or falls.
What flow are you trying to get through this drain and as it is now does the water level get close to overflowing the tank?

With your drilled pvc what happens now if you turn the tube so the holes are lower in the tank?

yes as it is set up the water passes the little plastic lip that holds the glass top, but as i watch it, it doesnt seem to overflow but thats too high to sleep well at night haha.

I am in the process right now of putting 1 inch on, as far as rotating the holes it did not seem to help, i think as the holes go more under the pipe the less flow that enters in....

This is the water level regardless of how i rotate the holes, I currently have a 1/8 hole in my "T" how can i lower the level?


[IMG]<a href="http://s64.photobucket.com/albums/h200/hyrumbradshaw/?action=view&current=IMG_2294.jpg" target="_blank"><img src="http://i64.photobucket.com/albums/h200/hyrumbradshaw/IMG_2294.jpg" border="0" alt="Photobucket"></a>[/IMG]

how much is your return pump putting out after head loss calculations?

I have no idea what it even began with?? I bought it at home depot its a pond pump, bought it to help with water changes. but i do know it pumps more than any of my other pumps.

Ok I got it all figured out!

as i plug the pump in the water level goes pretty high, I wait for it to get close to the top then I cover the hole in the "T" on the back. THe water gets sucked down and lowers until air starts going thru the holes in the drain pipe (in tank). then I let go of the little hole and the water level stays low! Dont ask me how it works but it just does, I tried it about half a dozen times and it works beautifully!

I have the 3/4 bulkhead and upgraded all pvc to 1 inch. I think that helped!

Thank you to all those who gave me ideas here!

Don't shoot the messenger here but....most pond pumps are not salt safe. They use a metal impellor shaft that will corrode in salt water.

hmmm now that you mention that, I think it does have a metal shaft. CRAP! I thought I was done!

I have a rio 800 but im not sure thats big enough to spit at!
What pump do you recommend ? remember I only have 3/4 bulkhead..

I feel like i have a ticking time bomb in my tank.....

Your problem is a simple one.

Your pump is pumping more water into the tank than the diameter of the return paths most restrictive element can accommodate. Which in your case seems to be the I.D. of the bulkhead.

Is there a particular reason why you need so much water flow in your system?
If not, then your best bet (most economical) is to reduce the flow coming out of the pump. Do this either by adding a simple ball valve or by restricting the diameter of the tubing connected between the pumps output port and whatever you are using as a termination at the tank end.

Your second choice (more expensive) is to increase the diameter of the water path from (and including) the bulkhead to wherever the water is draining to (assuming it's into a sump below the display tank).

It's really no more complicated than that.

I had a 3/4 drain on a AC802 (2-300gph @ 4feets) and it was doing siphon, a flood wanting to happend.

I grinded the glass so I could use 1" fitting, now my fitting still has room for more flow.

ok got the thing worked out but now I need to replace the pump any suggestions on a new pump for 3/4 bulkhead and i guess it will have about 5 feet of head

Why do you need to replace the pump? Is it broken?

As for a replacement suggestion, it really all depends on what you wish to accomplish with your set up. Some systems do better with a lot of flow, while some do better with less flow. But as a very general and generic guideline, a return water system flow rate would be around 5 to 10 times the volume of your system (per hour). As for brands, Eheim, Ocean Runner, and Pentair get my vote.

he need to have around 150gph max as a 3/4 return won't handle a lot more safely.

Try an AC402

[QUOTE][i]<a href=showthread.php?s=&postid=11556672#post11556672 target=_blank>Originally posted</a> by GuySmilie [/i]
[B]Why do you need to replace the pump? Is it broken?

As for a replacement suggestion, it really all depends on what you wish to accomplish with your set up. Some systems do better with a lot of flow, while some do better with less flow. But as a very general and generic guideline, a return water system flow rate would be around 5 to 10 times the volume of your system (per hour). As for brands, Eheim, Ocean Runner, and Pentair get my vote. [/B][/QUOTE]

The pump that is in there is a home depot pond pump, it has a metal shaft that is not "reef safe"

OK then, that makes sense.

Follow waht Guy said earlier. Whatever return pum you settle on, install a valve between the return pump and the tank so that you can "tune" your flow back into the tank to best match your drain.

As for the drain... you can increase the diameter of all your plumping to 6", drill 1000 holes, and it wont have any affect on the amount of water that goes through your 3/4" bulkhead. If you cannot/willnot increase the bulkhead, size the return as close as possible and tune with the valve until the desired water height. then adjust the noise using the hole on top of your "T".

I suggest drilling a single 1/4" hole on the T... attaching a 10" airline to the hole using silicone, with a standard airflow regulator on the end. you can now tune the airflow perfectly to the subtlety of your system and adjust later for when the pump performance degrades.

As ASM has explained,

The overflow will oscillate between full siphon and open channel flow. This can be stopped by prevent the full siphon from forming. However, it may also mean that the setup will NOT be able to handle the full flow of the return pump.

Anyway, there is a bigger problem. The overflow "looks nice" but is pretty much useless. In the current configuration there is NO surface skimming and even if half of the pipe was exposed, it would still not surface skim very well at all.

Honestly, I suggest an entire rework of the overflow. There needs to be an overflow box in place to provide proper surface skimming.

Folks, what looks "cool" does not always function efficiently.

beananimal how would you suggest i set it up with only one hole drilled in the back towards the top?

Just an overflow box and have it drain straight to the bulkhead with no attachments to the bulkhead inside the tank?

I would use a "calfo style" overflow to maximize the surface skimming. A down turned elbow in the box and a durso style standpipe (as explained by others) on the back.

A single bulkhead is certainly not the ideal setup from a failsafe standpoint. You can get it quiet with some tinkering... but it will always be prone to clogging that will case a system overflow!