PVC overflow ideas

[jbolinger]

Sorry for the ASCII graphics, but it was the quickest way I could get my idea on paper. If I actually build one of these I will provide more detailled drawings.

Idea #1 for surface skimming:

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Unfortunately it doesn't line up quite right. The arrows indicate where holes will be drilled. The outer tube is 2.5 inch PVC and the inner tube is 1 inch. The bottom of the 2.5 inch is capped. The bottom of the 1 inch is open. There is a 2.5 to 1 inch reducer at the top where the holes are drilled. The reducer is modified to allow the 1 inch pipe to slide all the way through. 1 inch tube open at bottom.

Idea #2 for filtering from deeper in the tank:

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Outer tube, 3 inch. Middle tube 2.5 inch. Inner tube 1 inch. There is a 3 to 1 inch reducer at the top and a 3 to 2.5 inch reducer at the bottom. As in idea #1 the reducers are modified to allow the smaller tubes to slide through. The 2.5 inch tube is capped at the bottom. In this version, holes are drilled near the bottom, as indicated by the arrows. 2.5 inch tube open at top. 1 inch tube open at bottom.

In both versions the outside of tank part is constructed the same as shown elsewhere (do a web or forum seach on 'PVC overflow' or 'PVC siphon').

Why do it this way? IMHO this would be less 'obtrusive' in a show tank.

Jim

[jbolinger]

Here's some better drawings, using Microsoft Paint:

#1

and #2

Jim

[tazcrash69]

Are you planning to hook one of these up to a canister, or is your tank drilled?
If it's for a filter, I strongly recommend the Fluval surface skimmer, works great, not obtrusive, and much smaller than 2" PVC for like $10.

[Naja002]

I don't understand the ASCII graphics, so I'm not really understanding what you are trying to do.

Have you checked out this thread yet?

Diy pvc overflow retrofit?

I use one of these and it works well. The option of greater flow would be nice, but the 1" pvc works good for a slow flow environment.

HTH

[jbolinger]

Originally Posted by Naja002

Have you checked out this thread yet?

Diy pvc overflow retrofit?

HTH

Yes, I've seen this. What size sump do you have? I think you would need a pretty good size one. If your return pump stopped, how much would the siphon empty the main tank? I only have room for a 10 gallon sump, so I have to make sure that the siphon can only dispense a couple of gallons if the retrun pump fails.

I just had the idea of only a single tube being visible, instead of a 'pretzel', as I've seen it called.

For the #1 design, the outer tube acts as a sump and the inner (1 inch) tube is the actual siphon. It does surface skimming.

For the #2 design, the outer 3 inch tube draws water from lower down in the tank. The middle 2.5 inch tube acts as a sump, and the inner 1 inch tube is the siphon.

Just and idea. I'll probably go with a normal 'pretzel' for my first shot at a DIY overflow. Its just that if using 1 inch PVC it can quickly take up a lot of room, IMHO.

Jim

[Naja002]

The bulk of the pretzel is hidden behind the tank. I have 1 1" outflow and 1 1" inflow pvc pipes showing in the tank--everything else is behind the tank.

My sump is a 45g tub with 3 different tank overflowing into it (and 3 return pumps--1 to each tank).

The amount of overflow when the pump (power) goes off is set by the horizontal pipe in the overflow pretzel. If you are not sure what I mean then you'll need to study that thread a bit. But I would say that there is a minimum placement--I just don't know where it is. Mine drains about 2-3" down at power-off--which is ok by me. The other 2 tanks are drilled, so they drop about an 1".

If You build one then you need to piece it together and get it working how you want it--before you glue it. That way if you want to lower the horizonatl bar (or even raise it) you'll still be able to make those adjustments.

The easiest way is just to drill the tank, but some folks don't want to go that route. Its very easy to do--provided that the glass is not tempered.

HTH

[Naja002]

Hope they don't mind me using and altering their photo, but here is the horizontal section that I am referring to:

[jbolinger]

Thanks, Naja002. That is what I thought you were talking about.

What type of flow rate do you get on the siphon?

I have seen several different variations of design on PVC overflows. SOme of them have the horizontal piece much lower. Either they have a much larger sump or some other means to limit the overflow. If there was a skimmer then wouldn't this stop the overflow siphon when the pump is off?

What do you think this one would do?



Jim

[Naja002]

I'm not an expert on this and there are others here that could probably be more certain, but if the pin hole allows enough air into the main overflow tube--the siphon will not restart. The pump will and flood the tank, but the overflow won't.

You're right, there are a number of variations on this theme. The reefers are the ones that have thought and experimented all of this through time and time again.

[jbolinger]

Originally Posted by Naja002

...if the pin hole allows enough air into the main overflow tube--the siphon will not restart. The pump will and flood the tank, but the overflow won't.

What I was thinking is that the 'pin hole' would be perhaps 1/8 inch, and the other holes would be 1/4 inch. There would be enough of the 1/4 inch holes so that their total area would be the same as the area of the 1 inch pipe.

If you compare this with a pretzel with a skimmer you will see that it has almost the same topology. If the level in the tank drops below the location of the pin hole then the siphon will stop, but there will still be water in the tube that goes over the side of the tank. So either I am completely out of my mind with this or the siphon should restart when the tank refills.

My idea is that, under normal operation, most of the water will flow through the larger holes and draw water from deeper in the tank.

Jim

[Naja002]

Originally Posted by jbolinger

If the level in the tank drops below the location of the pin hole then the siphon will stop, but there will still be water in the tube that goes over the side of the tank. So either I am completely out of my mind with this or the siphon should restart when the tank refills.

The problem is: when the pump /power is off the water level will decrease. As that occurs air will begin being sucked into the system via the pin hole. If there is enough air in the main overflow (where it actually goes over the tank rim) when the siphon is broken--then the siphon will actually be broken--completely, and it will not restart. The water in the main overflow portion must be maintained during a power outage--or the siphon will not restart. Hope this makes sense.....

Edit: I use the pin hole for the inflow/pump return line. It works great. I have a check valve also, but with the pin hole--the check valve really isn't necessary. The pin hole is at the water line (full) so when the pump turns off--the siphon is immediately broken. The water in the line drains back to the sump and that's it for that line. Prevents siphoning the tank into the sump via the drain line at power off.

The DIY PVC Overflow works very well as it is designed. There is a "skimmer" version, but that starts adding more "pretzel" inside the tank. One simple modification that I made was adding a cap and air line:

Pix are clickable:



This makes the system quiet.

You can DIY an overflow/skimmer box system like they sell and it can be done cheaply out of plastic containers and pvc. I did it a couple of yrs or so ago. But you wind up with more stuff in the tank, its gaudy and there really isn't much point. The overflow above works well. Only complaint would be slow flow--but for me its fine. I guessimate that the 1" pvc overflow that I use moves ~100gph. Maybe a bit more. But its on a 40g tank (2.5x/hr) and the tank is directly filtered with an xP3. So, its really not an issue for me.

I started out with the drilled hole concept for the strainers. Depending upon all the variables--they may clog or partially clog over time. I went to one of these for the overflow strainer (only because I had one from another project laying around), but if you have a miter/chop saw--they can be made very easily with pvc.