Building a Weir style Overflow

[dx7fd2]

Well, the next project to get this tank going is the weir. I used the plans from this site:

http://www.sparklingfloorservice.com/tank/overflow.html

I used 1/4" acrylic for the inside parts that I bent with a heat gun. It was slow but fairly easy. The side pieces I used were the 1/8" GE acrylite from HD. I would suggest building the whole thing from the 1/8" it is easier to bend.

I bought a real 1" bulkhead for $8, so the total cost was around $20. [smiley=2thumbsup.gif]

Here's a pic before the routing the whole thing. I will post a pic soon after I get the bulkhead.

[cannon2222]

It's looking good dx. If there was some way you could extend the sides that go over the tank wall, you could put in thumb screws, then you could adjust the water level in the tank.
It looks like the overflows that CPR make. If you go to their web page, you can see what I mean about the screws.
http://www.cpraquatic.com/products/overflows.html
Let us know how it works out.


phil

[JohnO]

I've always had a drilled tank in the past and am not that familiar with these overflows.

I assume it works by syphon? *If so, how do you match the return water flow?

John

[dx7fd2]

Cannon, I think I can take care of that either with the thumbscrews or just boosting the lip up that goes over the tank with a piece of plastic, cut to the specific height that I want the water depth to be. The size of the U going over the tank is just perfect so it would not be a problem to boost the whole weir up from the part that sticks out of the tank at the back.

John, yeah it works by siphon, and from the research I have done the 1" bulkhead I will be using should more than match the flow of the pump. We will see!! If not than a bigger bulkhead. Because there is no siphon tube the water flow is actually over the whole width of the weir which is 8". If it doesn't work...back to the drawing board. I think it will work.

[dx7fd2]

The link that Cannon put up for the CPR overflow has the same basic design, and according to the link the 8" width with a 1" bulkhead will run 600GPH. If I don't get enough flow I guess I make one 10" wide with a 1.5" bulkhead, or use two(I don't think I want to do that).

[JohnO]

[quote author=dx7fd2 link=board=DIY;num=1088694760;start=0#3 date=07/01/04 at 18:32:10]John, yeah it works by siphon, and from the research I have done the 1" bulkhead I will be using should more than match the flow of the pump. We will see!! If not than a bigger bulkhead. Because there is no siphon tube the water flow is actually over the whole width of the weir which is 8". If it doesn't work...back to the drawing board. I think it will work. [/quote]

Thanks for that :-)

What happens if the syphon volume is greater than the return volume? I would assume, if that was the case, that the tank would slowly empty and the sump slowly fill. Once the tank water empties enough wouldn't the syphon then stop?

John

[dx7fd2]

The siphon will stop as soon as the water level in the tank is below the section of the overflow that is in the tank which in this case will be somewhere around 2". Also as you raise or lower the weir this also affects the depth of the water in the tank.

[JohnO]

OK, I understand that part, but once the level has dropped and the syphon stops, what stops the return pump? Wouldn't it just keep going and either cause the main tank to overflow? Either that or pump all the water out of the sump thereby causing other damage?

John

[Matt Rogers]

John I would think it would like any other overflow and the pump would raise the water starting the overflow again.

I don't know about this one - VERY COOL, NICE JOB BY THE WAY DX - but the problem with some hang-on overflows is air gets trapped inside, preventing the siphon and causing the pump to pump all the water out of the sump. This may happen even if the siphon and pump never stop and it's working continously just from air being drawn in.

It usually takes a while - days - and you catch it before it's a problem. Some have holes and tubing at the top of the bend so you can draw the air out. The old style ones with the u tubes you just stick some airline up to the bend and suck it out.

Some people have safety switches on the sump pump to turn it off if the water in the sump gets too high or low which will prevent flooding too.

[JohnO]

Thanks Matt,

The reason I was asking is simply that I am not familiar with this style of overflow :-)

I still don't understand how it could restart by itself though as the part the water flows over ( the bend ) would be higher than the sides of the tank.

John