Back Siphon On Return Problem

[weaponsofmassdesign]

I am getting a back siphon on my return. It's going up my loc line down the return pipe and coming out of my Mag 18. How can I stop this? Can I drill a small hole in the PVC above the water line? Are there other ways to fix this?

P.S. I think we need a plumbing section on R2R!

 

[mfdrookie516]

Yeah, just drill a hole right below the water line... just be mindful of placement, as it may spray out of the tank if you've had your pump off. I also like running a check valve as well. I don't rely on it 100%, but it does keep all the water in the pipe, reducing the amount of bubbles and gunk that comes up when I kick the pump back on

 

[AZDesertRat]

Drilled holes, just like check valves, are a false sense of security and can and will fill, its not a matter of if but when. You can clean the hole this afternoon and who is to say a flake of food does not cover it as soon as you walk away, or a piece of algae, snail, anemone, small fish etc?

Place your returns just slightly below the surface so only a small, very easily calculated amount of display water siphons back before the siphon breaks and flow stops. This is called an air gap and is the ONLY foolproof method of backflow prevention, requires zero maintanance and cannot fail since water cannot jump uphill.

In my 60"Lx18"Wx23" deep 100G my returns are 3/4" below the surface. So 60"x18"x.75"/231=3.5 gallons. That means a maximum of 3.5 gallons is all that can possible siphon back to the sump worst case as long as the return is no deeper than 3/4" and I always maintain at least that much freeboard or spare room in my sump at all times. I actually have around 8 gallons of room in my 30G sump as that is where the baffles are placed and where the skimmer works best so I can never flood from a back siphon. Foolproof and no mainenance, it does not get any beter.

 

[weaponsofmassdesign]

Okay so I drilled the holes just below water surface in the return pipes and I raised the locline up where the water surface drops past them when the pump is cut off. Both have helped. I still have a check valve to add. I am still getting some slow drain from the returns. I have the dry side glued under the cabinet. I did not glue the return pipe to the bulkhead on the wet side inside the overflow box. Is this where it could be coming from and do I need to glue these? I didn't glue them incase I need to replace or clean them.

 

[AZDesertRat]

Do you have any photos we could look at? It would help.

Personally I will not own slip bulkheads, I use only thread x thread so they can be sealed well but still able to disassemble if needed.

How low are the bulkheads and Loc Lines in the tank? Loc Line is not always water tight, especially once you get corraline growth on it then move it around so the sections do not seal tight any more.

If things are done correctly you should never ever need either drilled holes or check valves, especially check valves which are a disaster waithing to happen.
I prefer to do it right the first time so I don't have to prop things up with holes and checks and it allows me to sleep soundly at night without fear of floods. If it is worth doing, it is worth doing right the first time.

 

[weaponsofmassdesign]

I'll post some pics of all my plumbing when I get home. I'd rather not use the check valve myself.

 

[btkrausen]

I generally place my returns right at the water line, or like 1/4 inch below it. It allows the return water to create some movement as well as prevent much water from being back siphoning when you turn off the return. Right now, on my display tank, I'm not doing this since the return comes out of the locline so fast that it pulls water from the surface. I think I need larger outlets or larger locline in general.

 

[jcharrsn]

I have seen black airline tubing coming from the back of the PVC at the top of the return plumbing used for siphon break, which I thought was a pretty solid idea. No light transmission through the tube so algae growth should not be an issue. You can point the airline tubing anywhere so that spray is controlled. That being said, AZ you are correct about the full proof safeguard from flooding keeping room in your sump and keeping returns to the display high. Mine are right at the water surface

 

[weaponsofmassdesign]

Okay here are some pics of what I have.

The return area of my sump with the return pump. The valve is currently in the closed position so it doesn't flood the sump while I'm gone.

From the pump it goes straight up and splits here.

The other end.

Here are the loclines.

And here are the return pipes. In the second one you can see how far down it drains the overflow box. These return pipes are slip and are not glued to the bulkhead.

Hope this helps figure out my problem. I haven't added the check valve and I would really rather not.

On a side note why would the check valve be a disaster waiting to happen?

 

[thewackyreefer]

I agree you should just allow a little back flow, ensuring the sump has enough space to take on the water. Check valves get clogged and just generally aren't very reliable in my experience.

I don't have any holes drilled in my return or a check valve.

 

[AZDesertRat]

Nothing I see in the photos is a problem or unique. What size is your sump and how much water do you keep in it while it is running? I don't see sump pics but I can guess you are running the sump level too high so don't have sufficient freeboard or capacity for backflow.

As an example, my display is a 100G and the Loc Lines are set 3/4" below the water level, about the same as the teeth on the internal overflow box. The tank is 60"x18" so 60x18x.75(the depth of the returns)= 810, 810/231= 3.5 gallons maximum that can possibly flow back to the sump before the returns are completely exposed to atmosphere and the siphon breaks.
My sump is a 30G all glass aquarium and I have found my sump works best when I keep about 20 gallons in it so I have 10 gallons of spare room or freeboard at all times. I never ever fill past that point even if I am going away or doing top offs manually.

Hiding 3.5 gallons of tank water in 10 gallons of spare room is never a problem and I never have to worry about a flood since water cannot jump uphill and my returns are exposed after only 3.5 gallons so flooding from backflow is not possible. An air gap is the best, most foolproof method of backflow prevention or to stop a siohonage there is. No check valves, no drilled holes and bets of all nothing to maintain or fail ever!

 

[weaponsofmassdesign]

Here is a pic of my sump. It is a 40g breeder.

I measured all three sections and calculated that it holds almost right at 30 gallons running. Here are the measurements for each section:
Drain Section: 18x6x14.5
Middle Section: 18x22x12
Return Section: 18x6x6(what I would like to keep the level at. It needs about 3.5 in. to run.)

I can cut the baffles down to make more room, but I think part of the problem is the return pipes inside the overflow aren't glued to the bulkheads on that side. Reason being after leaving everything alone for a couple days one of the overflows completely drained. Does that sound right? Should I also glue these or maybe go with threaded parts?

Thanks a lot for helping me out on this! I'm ready to get this thing going!

 

[weaponsofmassdesign]

Also, my display is a 165g with dimensions 72x20x27. I'll have to figure out how much is draining from it.

 

[AZDesertRat]

Your display holds about 6.25 gallons per inch of tank so with only 10 gallons of room in your sump you are borderline. I would cut the baffles down so the sump runs not much more than half full so you have at least 12 to 15 gallons of feeboard myself. As for slip bulkheds I have expressed my extreme distaste for them many many times, especially in my Bulkhead Installation Tips sticky. I downright hate them in fact.
But even then, if your overflow boxes are well sealed it will only drain the volume in the box and not the display so calculate the volume of the overflow area and add that to the freeboard in the sump.

 

[blackx-runner]

Sounds like one of your bulkhead connections is leaking water back. Your using slip connections and not cementing them? I would glue them up, or switch them out for threaded bulkheads. Also figure out that volume of water in the overflow and try to make room for that in the sump.

 

[weaponsofmassdesign]

Thanks guys!!

 

[mcarroll]

Just to throw my $0.02 in... (I hope this isn't too far off topic.)

First, the relative level of your overflow weir to your return flow outlet is your main, best way to control the amount of backflow to your sump, and where you want to start your accounting for the "extra" water. If you can do it all right there, great.

However, I'm a big fan a home-built spraybars for my return flow and they usually run all the way to the tank bottom. As a result, I sorta live by drilled air-gaps - since the 90's. There's nothing wrong with positioning your returns at the water line so they become a natural air gap, but experience tells me there's also nothing wrong with drilling air gaps if you need to.

A) drill them so they angle down toward the water - when they run exposed for any reason, the water doesn't shoot out of the tank.
B) drill two or three small holes around the perimeter of your return plumbing at or just under the water line. Blockage should pretty much be a non-issue.

That said, I'm also a big fan of big sumps (hopefully 100% of the size of the display) where 50% of their volume is empty for overflow mishaps - **** happens, I'll guarantee it. (The "big sump" plan paid off.)

;-)

BTW, I've never personally used a check valve, but I've seen an awful lot of them in action and I have yet to see a problem with one getting stuck... Some were even on systems that were known to have elephant slugs and the occasional anemone roaming the plumbing pretty freely. YMMV as always, but I'm not sure what scenarios lead to one of these getting stuck in practice. All the ones I've seen in actual use were plastic-flapper style checks like this one: Aquatic Eco-Systems: Aquarium Supplies - True Union Swing Check Valves Mechanically, it's pretty much the same thing as the check valve on my house's sump pump outlet - and that handles water with physical debris in it like leaves. I've not had one of these stick on my either - they should be pretty bullet proof in most circumstances. (Screen your return openings if they are large enough for any critters to get in.)

OTOH, I personally don't see the point of keeping all the water in the pipe during a power-off anyway, so if you have the choice I wouldn't add a check valve anyway. I might even go so far as to say that if you *really* need a check valve then you very likely have incorrectly over-sized the display tank. (Just speaking in general, not of the OP.)

Good luck knocking out your drainage problem!!

-Matt

 

[weaponsofmassdesign]

Problem solved! And I have enough room in my sump as is! Bought to get this 165 underway!!

 

[Retired_AF]

I have my returns set just below the surface of my dt. When I set up my water levels I filled my dt letting the water drain into the sump to about 1 inch below the lip with everything turned off. I then turned on my pump and skimmer and waited until the water levels stabilized. In the return section of the sump I marked the water level and that became my max fill line. I started taking water out until the pump started pulling air, then put enough in to raise the level just over an inch. I marked that point, making it my minimum fill line. Now, I just keep the water level between the lines and I know that a power loss will not flood my house. (I assume that is at least part your concern with the back siphon)

I do have a ball valve in my return line. I did that for when (not if, when) my pump needs replacing.

 

[neltel_7]

Drilled holes, just like check valves, are a false sense of security and can and will fill, its not a matter of if but when. You can clean the hole this afternoon and who is to say a flake of food does not cover it as soon as you walk away, or a piece of algae, snail, anemone, small fish etc?

Place your returns just slightly below the surface so only a small, very easily calculated amount of display water siphons back before the siphon breaks and flow stops. This is called an air gap and is the ONLY foolproof method of backflow prevention, requires zero maintanance and cannot fail since water cannot jump uphill.

In my 60"Lx18"Wx23" deep 100G my returns are 3/4" below the surface. So 60"x18"x.75"/231=3.5 gallons. That means a maximum of 3.5 gallons is all that can possible siphon back to the sump worst case as long as the return is no deeper than 3/4" and I always maintain at least that much freeboard or spare room in my sump at all times. I actually have around 8 gallons of room in my 30G sump as that is where the baffles are placed and where the skimmer works best so I can never flood from a back siphon. Foolproof and no mainenance, it does not get any beter.

I know this was posted a long time ago but I am plumbing my tank and was wondering why not just have the loc line sit just above the water surface? that way no water can get sucked up