Red sea ATO Syphon issue

strykerdog11 · Aug 4, 2025

Hey guys I have a red sea ato, and a max nano AIO tank. The ato is creating a syphon when I test it. The syphon break it at the top of the ato reviser. Im not sure exactly what im doing wrong here? Should the syphon break be somewhere else? This is may just be a stupid question.

Troylee · Aug 5, 2025

strykerdog11 said:
Hey guys I have a red sea ato, and a max nano AIO tank. The ato is creating a syphon when I test it. The syphon break it at the top of the ato reviser. Im not sure exactly what im doing wrong here? Should the syphon break be somewhere else? This is may just be a stupid question.

Do you have the siphon break installed in the correct direction? I’m not to familiar with the Red Sea one but others have an arrow… I’m not really fond of any of those ones that come standard with any top off! Me personally I install a tee from ro lines in my top off at the very top inside the container… the bigger hole prevents clogging issues and mishaps.

Gumbies R Us · Aug 5, 2025

Honestly, I got rid of my ATO that came with my Red Sea AIO. I ended up investing in a TUNZE ATO and don't regret it!

X-37B · Aug 20, 2025

You dont need a siphon break on an ato line. Just make sure the end of the tube is not under water.
Also the rs ato is garbage. I run Tunze on my rs

Troylee · Aug 20, 2025

X-37B said:
You dont need a siphon break on an ato line. Just make sure the end of the tube is not under water.
Also the rs ato is garbage. I run Tunze on my rs

I’ve always needed a siphon break on mine.. my top off water level is a foot higher than my sump water level. For what ever reason it siphons till the water level in my top off is below the sump…

. I thought it was weird the brand new tunze 3 didn’t come with one but I had a siphon issue immediately and had to add a break in the line.

X-37B · Aug 20, 2025

Troylee said:
I’ve always needed a siphon break on mine.. my top off water level is a foot higher than my sump water level. For what ever reason it siphons till the water level in my top off is below the sump… . I thought it was weird the brand new tunze 3 didn’t come with one but I had a siphon issue immediately and had to add a break in the line.

That does not make sense, but does not mean its not happening.
All 3 of my atos are a foot higher than the 7" sumps water level on 3 systems. I have no siphon happening on 3 Tunze atos.
If that's occurring you could use a check valve to stop back flow.
Still does not make sense as the ato is pulling from the bottom.

Troylee · Aug 20, 2025

X-37B said:
That does not make sense, but does not mean its not happening.
All 3 of my atos are a foot higher than the 7" sumps water level on 3 systems. I have no siphon happening on 3 Tunze atos.
If that's occurring you could use a check valve to stop back flow.
Still does not make sense as the ato is pulling from the bottom.

Correct… it doesn’t back siphon it just keeps draining my topoff after the pump offs… I’ve tried running the lines higher in my stand to stop it and it doesn’t.. it was easier to throw a 3 way ro coupler in the top of my top off container so it breaks all siphons in any direction.

X-37B · Aug 20, 2025

Troylee said:
Correct… it doesn’t back siphon it just keeps draining my topoff after the pump offs… I’ve tried running the lines higher in my stand to stop it and it doesn’t.. it was easier to throw a 3 way ro coupler in the top of my top off container so it breaks all siphons in any direction.

Well that's interesting anyway.
I will keep an eye on mine.
When mine shuts off it just stops.
No back flow or siphoning.
I have one going all the way up on my aio and it too just stops with no back flow either.

So with no break how much will it siphon out of the ato?

Just trying to understand in case it happens to mine.

Troylee · Aug 20, 2025

X-37B said:
Well that's interesting anyway.
I will keep an eye on mine.
When mine shuts off it just stops.
No back flow or siphoning.
I have one going all the way up on my aio and it too just stops with no back flow either.

So with no break how much will it siphon out of the ato?

Just trying to understand in case it happens to mine.

It’s the craziest thing lol.. it’s done it with cheap aqua auto top offs and the older tunze and now the brand new one.. my top off container is 24” tall and filled to the brim and my sump runs 10” deep.. without that siphon break it will drain my top off container down till it’s level with the sump water level. How or why idk since the tanks aren’t connected or anything. I’ve done this 3way break since the early 2000’s cause it was always a issue.. the aqua auto comes with a tiny valve that clogs super easily so even that one I upgraded to a ro fitting to prevent this problem.. I’ll take some pictures when I get home.

X-37B · Aug 20, 2025

I went back and read the Tunze instructions. It says the refill container should not be above the outlet height and mine are.

X-37B · Aug 20, 2025

Troylee said:
It’s the craziest thing lol.. it’s done it with cheap aqua auto top offs and the older tunze and now the brand new one.. my top off container is 24” tall and filled to the brim and my sump runs 10” deep.. without that siphon break it will drain my top off container down till it’s level with the sump water level. How or why idk since the tanks aren’t connected or anything. I’ve done this 3way break since the early 2000’s cause it was always a issue.. the aqua auto comes with a tiny valve that clogs super easily so even that one I upgraded to a ro fitting to prevent this problem.. I’ll take some pictures when I get home.

@rvitko
I will hit up Roger as all my reservoirs are higher than my sumps level.
Roger can you comment on this. Thanks.

Troylee · Aug 20, 2025

X-37B said:
@rvitko
I will hit up Roger as all my reservoirs are higher than my sumps level.
Roger can you comment on this. Thanks.

Yeah it sounds like you’ve been lucky lol.. obviously the pump is in the bottom of the container which is level with the floor of the sump but in my experience it doesn’t matter.. I already got a head ache from work but I’m sure @BeanAnimal prolly knows the physics involved.. haha!

BeanAnimal · Aug 20, 2025

Any time the open end of the discharge is below the level of the container that it comes from, then a siphon can occur.

In the case that the tube is submerged in the sump and the container, then a siphon can occur in either direction, from higher head to lower head until they are equal.

So let's take the ATO pool higher than the sump. Pump turns off, water keeps flowing until sump level reaches ATO level or ATO runs runs dry.

On the other hand if the ATO head is LOWER than the sump head, when the pump turns off, water may stop, but if there is ANY back flow (or the sump level rises for some reason or ATO level falls) then water will start to flow from the sump to the ATO, again until it finds its own level.