HOB PVC overflow with no box.

Gordonious

Active member
Iââ"šÂ¬Ã¢"žÂ¢m trying to find some posts,(as well as some sites) I used to have bookmarked. The posts were about a HOB PVC overflow. No box, just a series of PVC tubes. I will try to post pictures of what I have made so far soon, but it just isnââ"šÂ¬Ã¢"žÂ¢t working. I lost all my old bookmarks and though I read the post all the way through I never posted on it myself so it isnââ"šÂ¬Ã¢"žÂ¢t on my list of old posted forums.

Jon Gordon
 
I think I know what you are talking about and that thing scared the crap out of me. Why not just get a regular U-Tube overflow box?
 
If you read the forums about them you would know why.
1. Less space needed behind the tank.
2. Supposedly less risky during power outages.
3. No siphon = no lose of siphon.
4. I have PVC pipe and fittings.
5. I have what I thought would work and it probably only needs a minor change to get it working right, just stumped at the moment.
 
ive actualy been thinking of doing the same thing so that i could put a sump on my eclipse tank. if you are able to find it, could you please post a link?
 
wow!!1 thats realy cool! not exactly what i was thinking of but it could use that as a base plan. i also am looking to get one for my 40 gallon reef also.
does anyone know how well they work?
 
From whayt I have heard they are rock solid, quiet, and will easily flow 600gph+.. Anything over 600gph I would personally reccomend going to 1.1/2" pipe
 
OMG, those things look like an octopus! Remember that you will still have a siphon, so be very sure that it holds when your power goes out.

The one problem I would anticipate with doing this with PVC would be the use of the 90-degree turns and the likelihood that air bubbles would build up and the highest point.

This is the reason that CPR overflows require suction to be applied to them, to remove these bubbles which could eventually break the siphon. The U-tube designed overflows will clear bubbles themselves. Maybe it is possible to bend PVC into U-tubes to avoid the elbows: I don't know.
 
Those are the exact two links I was looking for, thanks everyone.

The <A HREF="http://www.nd.edu/~lego/grp2/www/reef_diy.htm">first link</A> is just about exactly what I did. Though there is two pipes heading down into the sump, I had put a stopper in one and was only using the other, I wonder if you have to use both. Going to try.

As far as air getting trapped, we came up with an idea. Where the air escape is in the first one, as well as the tallest point(the 45* turn) we placed air check valves in them so that air could go out. Then someone came up with a bright idea of attaching airline tubing to the check valves and attaching them to power heads, to actually pull air out.

I tried this, but wasn't getting much pull, so I built something into my return pipes that I thought would create a vacuum as the water was going up, and well that didn't seem to work either. My last idea was to try to use an air pump to create a vacuum, and I have not had success doing this with just a bucket of water and air line tubing.

Mine will have to be full proof before I leave it running as I am a college student and may not come home for 3 weeks at a time. I will have the extra little help of some battery back ups though, but they will only last about 2 minutes max. (the money isn't there for anything better)

Jon Gordon
 
You do need to use both pipes heading down to the sump, but you could "T" them back together.

This will keep both sides of the overflow equal.

As far as drawing air our of that 45... get an aqualifter pump.. you dont need to suck much out of there, and I haven't heard of air getting trapped there..
 
I love Reef Central. fareforce, thank you very much for your response. I tried it out with both of the outlets and it worked perfectly. I've looked for something like that aqualifter pump many times before and came up with out anything. I am probably going to order one from Foster and Smith tonight.

Jon Gordon
 
<a href=showthread.php?s=&postid=6505546#post6505546 target=_blank>Originally posted</a> by Gordonious
If you read the forums about them you would know why.

2. Supposedly less risky during power outages.
3. No siphon = no lose of siphon.

2 - why is this?
3 - how does it not have a siphon when it has to go over the top of the tank?
 
Read the forums. The siphon on a normal u-tube is lost with in 3 seconds of the water level going below it's range. Using the HOB PVC I would say it takes at least 5 minutes. Most power outages are a quick blink, and like I said I have battery back ups as well. in order to get the thing running after it has been left for an hour with out any water moving through it takes a half second prime at the highest point and it starts quick.

Adding the aqualifter pump, I don't think there is a way that it would stop unless you made it stop. It would basically prime itself, and with as many inlets and drainage tubes as there is, as wide as it is all the time, it would be ridiculously hard to plug up.


I am not going to go into any more detail then that because this has been debated for weeks at a time before on the other forum. There were about 4 other forums as well that were off on the side and all ended up linking back.

If your really curious, try it. Use an empty tank and a bucket.

Jon
 
<a href=showthread.php?s=&postid=6512132#post6512132 target=_blank>Originally posted</a> by Gordonious
Read the forums. The siphon on a normal u-tube is lost with in 3 seconds of the water level going below it's range.
Not true. A U Tube overflow does not lose siphon.
Using the HOB PVC I would say it takes at least 5 minutes.
That would be very bad. It should never lose siphon
If your really curious, try it. Use an empty tank and a bucket.

Jon
I power off my system every day when feeding. Never a problem. I've had it powered down for days when adding a new sump as well.

I think you need to read up on how a siphon overflow works. A good starting point is the ends of a U Tube are submerged at all times whether power is on or off. The drain box side is done with either a baffle or a tall standpipe. No air can enter the U Tube and siphon is not broken. This is how all U Tube overflows work.

Why in the world would anyone design or buy an overflow that doesn't work after a power failure?
 
<a href=showthread.php?s=&postid=6512132#post6512132 target=_blank>Originally posted</a> by Gordonious
Read the forums. The siphon on a normal u-tube is lost with in 3 seconds of the water level going below it's range. Using the HOB PVC I would say it takes at least 5 minutes. Most power outages are a quick blink, and like I said I have battery back ups as well. in order to get the thing running after it has been left for an hour with out any water moving through it takes a half second prime at the highest point and it starts quick.

Adding the aqualifter pump, I don't think there is a way that it would stop unless you made it stop. It would basically prime itself, and with as many inlets and drainage tubes as there is, as wide as it is all the time, it would be ridiculously hard to plug up.

Jon

Why not just use a normal U-tube overflow, once the syphon is started, it will not loose syphon so long as the U-tube stays submerged which there is not reason it shouldn't if the both boxes were made right. No airpump needed like this one and the CPR ones.

And just remeber, if you air pump fails and doesn't start the syphon, then the hole system fails and your return pump will pump all the water out of your sump overflowing your tank... or if you have an auto top off system, as water if overflowing your tank, it will continue to top off your sump until its resievor is empty causing a big drop in salinity too.
 
I am not against the PVC idea, but you have to realize that it has some important potential drawbacks.

As I mentioned in an earlier post, you have to use a separate means to remove trapped bubbles.

The aqualifter is probably the best solution to this, but aqualifter pumps are not perfect and actually I have found them prone to failure. They plug up quite easily and reduce or stop sucking. I had to take mine completely apart once to get it back to working order. About every 2 weeks I had to blow into the uptake tube to clear it out. Maybe I had a bad model, I don't know - but realize this is a point of failure.

While it is true that "The siphon on a normal u-tube is lost with in 3 seconds of the water level going below it's range", the fact is that on a good U-tube overflow, it is designed to NEVER let the water go down this far. Usually there is a baffel present or an extension tube on the overflow which maintains a minimum water level, higher than the bottom of the U-tube. Also, the lack of corners in the U-tube means that air bubbles can travel through and out of the tube, so even if there are some bubbles entering, it will clear them.

I am coming from the experience of running a CPR overflow for 9 months, which is functionally equivalent to the PVC designs linked above in that it has 90-degree angles and requires an aqualifter or similar. I spent a good bit of time worrying that the suction from the pump would fail. I eventually bought a good U-tube overflow and have eliminated one more pump to plug in.

I realize that any overflow design can fail, but in general, I think a good U-tube is more reliable than the CPR/PVC overflow design since it does not rely on a pump to maintain the siphon.

If you want an extra-safe overflow, get a U-tube one and then add a hole at the very top connected to an aqualifter pump.

My next tank will definately be reef ready or drilled to eliminate this potential failure (and lower the risk of flooding).
 
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