Siphon Break Idea on Main Return

[Modo]

I had my new 90g tank drilled for two returns about 3" below the water surface. Once I started planning and setting up everything I realized that during a power outage or when the pump shuts down I will have a major amount of water siphoning off. So, I came up with a design that I hope some of you can comment on. I'll try and explain to the best of my ability here.

From the main return I plumbed the pipe above the water level and installed a tee. then plumbed back down to the returns to branch out to the bulkheads on the back of the tank. Then I installed a 1/4" John Guest tube fitting on the tee. Inserted a length of 1/4" tubing and fixed it to the rim of the tank so it will extend just about a 1/4" below the water's surface.

My theory is if power is cut to the pump the siphon will be broken by the air from the 1/4" tubing. The bulkheads will not be able to drain off once the siphon is broken because the pipe was plumbed slightly above the tank's water level. So, as long as I keep the tubing clean I should be safe from flooding my sump.

Can anyone see any flaws with this design or thought? Will the 1/4" tubing once exposed be able to draw in enough air to break the siphon? I have not tested this on the tank yet because I'm not ready to add water. But, if there is some error in my thinking now is the best time to correct it.

Thanks all!!
Kurt

 

[taikonaut]

Sounds OK.... a pic will be great. But make sure the 1/4 tubing does not get clog up during the "good times" and won't suck in when you really need it to work.

 

[Juck]

Sounds interesting,, would like to see a pic/diag.

I prefer drain & return holes in the back pane,,,I have a similar setup on my 75 but my fuge is big enough to take the water during a power cut,, which happens all the time where I live.

I recently installed a flow valve on the return 'cos I had one hanging about,,, works fine though I don't really need it,,, might be worth considering for your setup.

 

[Modo]

Here is a very rough sketch of what I am trying to describe. Let me know if it is confusing.

 

[royy]

To save some time doing the plumbing over, just drill a hole about 1/4 of an inch below the surface of the water. This will suck in the air. Just make sure it doesn't get blocked with coraline.

Roy

 

[Modo]

All the plumbing is external, the only thing in the tank is the output of the bulkhead and some fan nozzles.

I've done what you are describing in the past, but not so lucky this time. :?

 

[royy]

Oh, I see how that can suck. Just out of curiosity, why didn't you use an overflow? Doesn't the top later of water get nasty?

Roy

 

[Modo]

The tank does have an overflow, I just didn't add it into the diagram. From my original post I'm mainly concerned with the siphon of the return when the pump shuts down.

You'll see at the bottom of the sketch an arrow pointing towards the pump labeled "Intake".

 

[Juck]

Seems a lot of work compared to a simple flow valve on the return pipe.

 

[Modo]

What do you mean by flow valve? Do you mean a back-flow or check valve?

It really wasn't a whole lotta work. Just 2 additional 90s a tee and a John-Guest fitting that I had laying around from when I made a Calcium Reactor. Added maybe 5 mins to my total plumbing time. Remember I haven't added water to the tank yet.

I may run the tubing over to my overflow box so it can be out of the water vs. below the surface. This way when I do my daily check-list I can see if the tubing is not clogged by just viewing the flow of water out of the tube.

 

[Juck]

Yeh,, a check valve thingy,,, they restrict the flow a little bit but not as much as the extra height and angles in the diagram.

 

[Anonymous]

I did the same thing, but added a check valve onto the end of the tube. The check vavle should open up in response to the back-pressure created by the shut down of your pumps. I suspect the check valve freezes up over time. Your way (without the check valve) is more fool proof.

In any event, I would still drill 1-2 holes (1/8" or 3/16") in each of the return pipes right at, slightly above, and/or slightly below the water line. These holes will act a back-up syphon breaks. Or perhaps I would consider these as the primary syphon breaks and the the tube as the back-up.

 

[Anonymous]

Check valves fail.... period. It's not a matter of "if". It's a matter of when, and Murphy being the optimist he is, you can count on it happening at the worst possible time. I learned this little piece of wisdom the very hardest way.

- Bert

 

[playfair]

I did the exact same thing you described on our public Seneca Park Zoo tank. Pipe size is 1.5", with 1/4" "bleed lines". Just be sure to check them often for clogging.

 

[Modo]

Longshot- That's exactly what I've been warned about over and over. One of the main reasons I went this way.

Playfair - Thats exactly how mine looks. Thanks for the pic. I'm glad to hear that they work especially on 1.5" pipe. Mine is half that diameter so that makes me feel much,much better! Now I can sleep well tonight or at least start to dwell on something else.

 

[Anonymous]

Seems like a good idea to me. A little extra work and money but still good.

 

[Anonymous]

Check valves fail.... period. It's not a matter of "if". It's a matter of when, and Murphy being the optimist he is, you can count on it happening at the worst possible time. I learned this little piece of wisdom the very hardest way.

- Bert

One minor difference is that a check valve used in the above-described manner is being used differently. Check vlaves are normally open, with fluid flowing through them. They can easily get clogged and refuse to close. In the above design, the check valve is normally closed with no fluid flowing through it. It should not get clogged and should therefore open in response to a vaccum.

 

[Anonymous]

Actually, if you want to make this impossibly foolproof, then have one of your returns right below the waterline. I did this on my 400g where I split the return from a large Sequence pump into 8 separate 3/4" returns spaced along the back of the tank. Although some of the returns exited at low as 30" below the waterline, 2 of the returns exited 1/2" below. The worst case scenario, if all of my anti-syphon holes are plugged, and my back-up check valve is frozen, is that the syphon will be broken as soon as the water line drops below these 2 returns.

 

[Len]

For the sake of searches in the appropriate forum, I'm moving this thread to DIY forum with a copy left in the GRD.

 

[GSchiemer]

Good idea. It should work. As others have suggested, just check the flow through the 1/4" tubing occasionally.

Greg