DIY Overflow build question

[Skeeter7424]

This is posed to those of your home-plumbers who have built your own overflows. I built an overflow out of acrylic, and before I secure it in the tank, I was wondering if there was a way to calculate max flow out of it. More specifically, can you calculate the flwo through a fixed number of specifically sized holes in the acrylic. I currently have 13 holes at 3/8" drilled in the overflow, and need to make sure it will flow enough to keep up with my return pump.

Also, if it matters, the return pump is a MJ1200. Its flow rate is 295 GPH at 0" head. This will be pumping approx. 30" up. I cannot find a flow chart for this pump, however I have seen that with the head height of this, it doesnt lose a lot of flow.

Thanks for the help, full build thread for this frag tank set up will follow in the next week or so. Gotta finish this, and the LED setup. Then the tank should be complete...for now...yeah right!

 

[JohnK]

I have no clue.

When in doubt, build a model - maybe cut identical holes in a 2 litre bottle then hook up the pump in a 5 gal bucket with the bottle above so it's pumping into the bottle and see if the holes can keep up?

 

[Skeeter7424]

John that is a great idea. I will try that tomorrow. I've been trying to figure out how to test the design!

 

[JohnK]

Just be sure that it can handle well more that the pump pushes at whatever head height. If it's just right, add some more holes to be safe.

How are you building his? Big PVC pipe cut in half to make a corner overflow? If you get stuck LMK and I can bang out an acrylic version for ya.

 

[Skeeter7424]

Nope, i actually made it all out of acrylic. I had a large sheet so I cut a piece, heated it, and formed it around a wood form I had made. I then cut the bottom out with the dremel and will be fusing it tomorrow. The tank is already drilled so this is just an overflow box. Its footprint is 5"wide x4"tall x4"deep. I also used my random orbital sander to "frost" then entire thing. Originally this was to prep it for paint, but not upon looking at it, I think I may leave it frosted. We'll see after its assembled. Also still have to make a removable top for it that I'll most likely black out, both for algae prevention and for noise removal...

Thanks again for the test idea.

 

[JohnK]

Got any pics?

 

[Skeeter7424]

Yup I have a bunch. I'm gonna put them all up when I finish the frag tank. Should be waterlogged by the beginning of next week.

Here is a teaser though. This was before it was drilled. And I sanded it again with the orbital to try to white it out a little more. Still going to sand it again because once water hits it it clears up a little...

 

[Skeeter7424]

This was the original form. I over-estimated A LOT. I cut about 4 inches off the first design after I test fitted it in the tank and could actually visualize what was going to happen.

Edit: You can also see where I overheated it a little bit. This was with a heat gun, and I stopped moving my hand with it to change a song on my Ipod...whoops. I will be investing in a heat wand to do more acrylic work...

 

[JohnK]

Looks good. Did you drill the holes around the top edge? If so, you could fairly easily extend them into slots with a dremel or a table saw. You could also let the water spill over the top of the pump is too much.

 

[Skeeter7424]

the holes are centered 3/4" from the top edge of the overflow. If need be I can extend them easy enough. I have a bunch of junk small plastic boxes at work that I am going to drill and use your test method on. The fallback will be water spilling over the top over the overflow, but I am trying to avoid that as it will be mounted as high as possible, touching the rim of the tank.

Again, this was a great learning experience with every part of the process. I have already decided to invest in a blade for my table saw to do acrylic, as I am all done using the dremel for large pieces. Especially when I can set the rip fence up on the table saw and repeat cuts. Any suggestions on a blade? Or is this not the way to go?

Thanks again John

 

[JohnK]

I've always gone the router route for edge prep, but meleves reef has some table saw blade suggestions. Otherwise you can get a blade that's made specifically for acrylic from usplastics among other places, but they cost something like $200 plus.

(routers are super cool tools, something to consider )

 

[Skeeter7424]

Yeah I have a router in the works. I am actually building a jig for it right into either my workbench or my table saw. Preferable the table saw, because then I could still use the rip fence and miter gauge that are trued into the table...

Weld-on 4 is the correct "glue" for this application correct?

 

[JohnK]

I'm already jelous, my table saw probably isn't up to the router add on

If you get a new router, consider one with a plunge base included. Priceless for making flanges (for Ca reactors and such) and also great for making overflow slots (without open tops which tend cause chipped teeth). Also, for applications where they will work, spiral cut bits make much nicer cuts/edges than standard straight flute bits.

WO#4 is probably the ideal off the shelf solvent for scratch buliding most anything we would want for the hobby. (pros often make their own solvents, but that's another topic). WO#16 is good for repairs or really rough work, not nearly as strong and comes out as a bubbly mess insted of nice clean seams.

 

[Skeeter7424]

So I ran the flow test, and heres what happened. I took a tennis ball container and drilled 3 holes in it. Turned the pump on, overflowed. Drilled 3 more holes. Overflowed. Drilled 3 more holes (now up to 9 holes on 3 different levels), overflowed but not very much. Drilled two more, ran perfectly. Drill the 2 remaining holes above that to see if water would get there, the two remaining hole (to make 13 which the overflow has) never got wet. Also, this test was performed at 0" head height, which it will not be operating at in the system.

So by my simply math...11 - 3/8" holes flow 295 GPH = each 3/8" holes flows 26.818 GPH approximately. I wouldnt use that number in some huge design, but for a baseline for people building overflows, it will work.

Going to HD in a couple to get WO4. Then I'm going to recut the bottom piece because I don't like how it came out originally. Then sand the whole thing again to further frost it, and assemble. Final sanding done tomorrow at work where I can use my air sander and our huge compressor. Then gluing it in the tank tomorrow night. Cant wait to have this up and running, I want my clownfish out of my sump

 

[JohnK]

Oh, sorry I've been snowboaring all day (could have save you the trip), You won't find WO#4 at HD or any other local place. Only a plastics supply place. Jfreeman in boston has some in stock that is NOT out of date (check the bottom of the can for a date, don't buy it if it's much more than a year old).

 

[Skeeter7424]

Yeah I found that out. I actually picked up a 2 part epoxy for now that will work for this. I am going to invest in a can of WO for future products that im going to make. For this being a low-pressure piece (and me having zero patience when I start a project...) the two part with work.

Also I found a 10" plastics blade on amazon for $70a that's made by diablo. Gonna buy that and start prototyping more of the things I have plans for!

Pics to follow

 

[JohnK]

I'd hold off on using the epoxy personally, but yea it probably will work. I can loan you some WO#4 if you want to pick it up, my car is in the shop at the moment.