Building a Weir style Overflow

[Matt Rogers]

True but remember it's a siphon. That back part of the bend goes lower than the front. When the siphon is halted when the pump goes off, it doesn't break it just holds. Dude now you are confusing me! Somebody help me!

[JohnO]

OK Matt, I think I understand what you are getting at but remember my initial questionwhich was how do you match the return water flow.

Correct me if the following statements are incorrect please.

If you get a container of water, place it on a table, put one end of a hose in the container and on end on the floor nothing will happen, no water flow.

If you suck on the tube end and get the water top flow over the edge of the container the water will keep on flowing until the container is empty due to effect of a syphon.

Now, the only thing that determines the long term flow rate is the length and internal diameter of the hose, correct ( unless of course you introduce some sort of valve )

If the above is correct, then my question still remains as you must most certainly have to have the same volume of water being pumped into the tank as is syphoned out or something other than the fish will get wet :-)

Please help, my brain hurts :-)

John

[dx7fd2]

The intention is to drill a small hole at the top of the section that goes over the tank and attach an airline to it that will also be attached to one of the Maxi-Jet venturi inputs there-by sucking any air out of the weir and creating continuous siphon. [smiley=yaknow.gif]

Also there is one additional piece I have yet to put in which is a 2" riser in the outside section of the weir this also maintains the siphon. I have not put the piece in yet 'cause I want to cut the side pieces with the router first. [smiley=builder2.gif]

When all finished I should be able to count on the weir maintaining its siphon constantly even if the water gets below the front of the wier. Of course, no water will flow until the return pump catches up. Not that that will be a problem, the pump I'll be using is a Mag9.5, plenty of water at 3'.

John, I neglected to mention that the return pump will have a tee on the output that will send water to a ball valve that goes back into the return section of the sump/fuge...this will enable me to regulate the flow between the weir and the return pump nicely... you can also add a ball valve onto the line going down from the overflow to the sump, if you need to...

Thanks you guys for your help and encouragement!! I feel pretty good that I am able to answer your questions. It makes me feel like this is going to work!!!

[smiley=2thumbsup.gif]

[Matt Rogers]

Drew you did a amazing job. I am really impressed. I know I couldn't have done such clean work. I'm a hack! Please post pics of it in action!

[quote author=JohnO link=board=DIY;num=1088694760;start=0#11 date=07/01/04 at 23:52:27]
If the above is correct, then my question still remains as you must most certainly have to have the same volume of water being pumped into the tank as is syphoned out or something other than the fish will get wet :-)
Please help, my brain hurts :-)
John
[/quote]

You are absolutely right sir! That is why hangon overflows are sold with GPH ratings, typically starting with 300 GPH, then going to 600 GPH, etc..

[dx7fd2]

Most of my experience is with wood. I build furniture, speaker cabinets, and stuff like that. It really helps when you have the tools and a shop set up for doing detail work.

I have collected a pretty good array of tools over the last 15 yrs!!

[JohnO]

Drew,

Thanks for explaining the use of the ball valve(s) to control the flow and as Matt already said, you have done an excellent job :-)

I have some more questions but they will probably be answered when you post some more pics :-)

John

John,
You don't have to worry about matching the flow rate because the water overflows from the tank much like your drilled tank. The difference is that it overflows into a reservoir inside the tank, the external side also has a reservoir with another overflow into the drain. When the pump stops the water level drops to the level of the overflows, both ends of the siphon stay submerged thus preventing a siphon break. When the pump starts up the water just starts overflowing again. As long as the flow rate of the pump doesn't exceed the capacity of the drain the water will return to the sump at the same rate as it is pumped into the tank.

There many different designs for hang-on overflows but (correct me if I'm wrong) I think they all work this way in one form or another.

Nice job Drew.
Wish I had that kind of talent!

Ted

[dx7fd2]

Ted,

You are exactly correct on the principals of the overflow. Good job!!

Why don't you become a member, it sounds like you belong here at 3Reef. [smiley=2thumbsup.gif]

Thanks for the compliment!!

If anybody is following this thread I will be posting more pictures of the Weir, Skimmer, Tank, Lighting, and Refugium when I get the tank set up and get a decent camera!!

[glow=red,2,300]3 Reef Forever[/glow]

[smiley=sunny.gif] [smiley=sunny.gif] [smiley=sunny.gif]

[inwall75]

I can't believe I missed this thread. Great job on the unit Drew and great info everyone.

[JohnO]

Hi Ted :-)

John,
You don't have to worry about matching the flow rate because the water overflows from the tank much like your drilled tank

Now I'm confused again. Thanks to the wonderful people here, who have been VERY patient explaining the principals and workings of the overflow, I now understand how it works with the use of ball valves ( etc ) as a way of matching the flows.

If you don't use some way of controlling either the return or the drain water, how can it work long term?

If the drain ( for example ) syphons at a rate of 10gallon per hour and your return pumps at 5 gallons per hour, what will happen? Also, what would happen if the opposite applied? I just can't see how this system could work without some way of controlling either the return or the drain.


John