Retrofit Oveflow: Overflow box vs. PVC Standpipe Discussion

[sdboers]

Hey Folks,
  Next DIY project for me will be a retrofit overflow for my 135g tank.  I don't want to get into drilling it for multiple reasons, so this will be a hang-on-back overflow.  I've seen countless examples of overflow boxes and ones constructed from PVC pipe and the web.  Both methods have their supporters and both methods seem to work.

  Does anyone have any experience with either of these methods?  Any recommendations as to which one works better / more reliably?

  From my perspective, I think the PVC pipe version will be cheaper and easier to build - kinda like working with lego.  The overflow box would be nicer looking, but a bit more costly and a bit more complicated to build - but nothing insurmountable.

  Thoughts? Really interested in people's opinions.

Sean.

[Carl]

The vast majority of my overflows were pre-drilled. I found not issues other than the drilling process itself.

As for HOB overflow boxes, most that I did use had siphons, which had many issues, especially with larger fish.

You indicated two methods of HOB over flows, could you be more specific?

Carl

[sdboers]

Carl - happy to elaborate on the two types I'm considering. Since they are retrofit - with no tank drilling - both versions rely on a siphon being created and maintained.  One safety mechanism that is easy to incorporate is a hole drilled into the highest part of the siphon tube with a check valve glued in.  Airline tubing is run from the check valve to the air intake on a powerhead.  If the worst happens - then the siphon is restarted by the powerhead removing any air from the siphon tube.

Version 1 is the PVC pipe version. I actually constructed one of these previously for doing overflow water changes (in with the new - out with the old!). My pipe choice was too small (1/2") so it's usefulness is limited. You can easily make these with dual inlets as well (redundant) for increased flow and safety.  Here is an excellent video that shows how one is constructed:

And another video that explains how it works:


Version 2 is the overflow box. There are many commercial versions available and a number of DIY variants.  Here is a commercial version:


And here is a link to a DIY version: www.aquariumlife.net/projects/diy-overflow/70.asp

Sean.

[Carl]

Thanks for sharing!

I definitely like the idea of the PVC model over the traditional HOB model (which is what I have primarily used when a tank is not pre-drilled).

The problem with the second/traditional HOB is that the the siphon was easily broken and interruptions in electricity were not always met with a re-start. For me, since most of these were at a client's home/office, this meant emergency visits, which if under contract was money out the window. In the end, since drilling an established aquarium was not usually an option, I often removed the sump and pursued other filter options, which by the 1990s meant FSB Filters.

The second option offers more promise IMO, although I would add a cap to the intake/overflow in the tank and then add several drilled holes as the overflow to prevent the intake of fish or debris that could disastrously clog your intake.
A double over flow would be a good idea as suggested in the video.

I would disagree with the flow rates, as I have gotten much higher flow rates out of the sizes of PVC he notes, probably about double.

I have employed the check valve with a power head in the older traditional HOB overflow, which is a good idea, but I can tell you from experience that this is NOT fail safe and again redundancy IS IMPORTANT!

Another though/caution is in case of siphon failure, make sure that your sump hold NO MORE WATER than will over flow the aquarium.
Example, if the sump holds 8 gallons, the volume your main aquarium holds ABOVE the siphon is NOT LESS THAN 8 GALLONS

Carl

[sdboers]

Yeah... NOTHING is fail proof!

Since my intent is to use this overflow in conjunction with a continuous water change, loss of siphon would be a slow problem (less than a gallon per hour), but potentially a large problem (one gallon per hour until someone noticed).

I would probably incorporate a float valve to the water supply to choke it off if it exceeded the level determined by the PVC standpipe...

For your larger flow rates - are you talking about gravity fed flow rates - or maximum flow rates? I think the flow rates mentioned are lower due to the fact that the pipe is essentially gravity based and surface skimming (air to contend with)... Am I right?

Sean.

[Carl]

Feb 25, 2015 14:13:34 GMT -5 sdboers said:

For your larger flow rates - are you talking about gravity fed flow rates - or maximum flow rates? I think the flow rates mentioned are lower due to the fact that the pipe is essentially gravity based and surface skimming (air to contend with)... Am I right?

A little of both.

You definitely can get at least triple under pressure, but as for gravity flow rates, I used mostly 3/4 and achieved much higher flow rates than described in the video

Carl

[sdboers]

Ok - I purchased the material to make the PVC pipe version. Hopefully I will get to it this weekend and will post in the DIY section. I went with 1" PVC - huge overkill - but better safe than wet... The material is white, so at some point I will probably paint it black or dark blue or some other unobtrusive color.

I also ran the plumbing last night from BEFORE the water softener, over to the tanks to get primed up for the automatic water change system...

Changing gears - got a chlorine question...
As you may (or may not) recall from previous posts - I've got a chlorination system in the house. Adjusted well and performing properly, there would be no chlorine left in the water being distributed to the rest of the house after it passes through all of the treatment equipment. There are times when there may be a small bit of residual chlorine left in the water. With a continuous water change system running at 1/2 gallon per hour on a 135g tank - I'm assuming this wouldn't really be an issue?

Sean.

[Carl]

Likely this would not be a problem.

I would suggest a Regular Wonder Shell, as besides the mineral Cation benefits, being a reducer it will counter any residual chlorine (I used these in ponds that had continuous water in and out that got ther water right out of the municipal tap, and never registered any chlorine)

Resource:
www.americanaquariumproducts.com/MedicatedWonderShell.html

Carl