Dual check valves in air pump line?

[T Waters]

Tank is 135 gallon (I would hate it all to empty on the floor where the pumps are)

Four airstones (for oxygenation, thus 4 air lines).

Check valves are cheap (about $1.25 each), so is it good idea to put two in each line in series? That way if one fails then the other might prevent any backwards water flow?

Or is this not a good idea for some reason?

[V227]

Having 2 check valves on one air line equals 2 cuts into the line. The more cuts in a line the weaker the link from the pump to the air stone. I think it would be okay to do it, but personally, I wouldn't.
I had a check valve malfunction while cleaning filters. Of course the power was turned off. The water siphoned back through the check valve down to the air pump. It didn't leak.
With the power back on, the pump pushed the water back through the valve back into the tank. I quickly changed the valve.

[T Waters]

ok, thanks, anybody else have thoughts?

[Fresh2o]

If the pump could be placed above the water line, then siphoning should not be an issue.
I don’t think a second check valve is a problem so long as the tubing is seated FIRMLY on the fittings.

[coralbandit]

Raise the line itself above the tank before routing it to under where the pump is .
That alone done properly will prevent syphoning.
I try to run my airlines as high as possible before returning it to pump.
I don't trust check valves [made for aquariums] one little bit .
You do get what you pay for more and more these days ..
$1.25 worth of protection huh ?

[T Waters]

Thanks, coralbandit. I'm going to do that based on your advice. The only negative is that the tank is prominently displayed in living room and I would have to attach something to the wall up above the tank to hold up the airlines and it would not look so good there. So now I have to figure out how to hide the tubing and the tubing holder .

[T Waters]

My filters have been pretty leakproof from the beginning since years ago, so late than never, now trying to get the air pumps reasonably leak proof

As others in this thread have guided me, I'm going to be using gravity to prevent reverse siphons in the first place.

Until the last 3 days, I knew virtually nothing about this, hence my questions. I guess I'm just also going to go along with this guy's suggested valves, which advice I found today online. He says the plastic ones on Amazon are not very good.

https://fishlab.com/air-check-valve/

His recommended for freshwater tanks not using ozone nor co2 :
https://www.usplastic.com/catalog/it...x?itemid=24234

He (guy on the first link) recommends other check valves than these for tanks with co2, lots of ozone, or saltwater tanks. But I don't have those type of tanks.

Viton vs. Buta-N seals

https://www.humphrey-products.com/co...r-applications

[T Waters]

And thanks again to the repliers who have put me straight about the real way to prevent hundreds of gallons of water doing thousands of dollars of damage to the living room carpet, floors, and walls of our home residence!

[T Waters]

OK, I received and am using the check valves in my link above from US Plastics: SMC 695 Series Mini Check Valves

They are completely different than the ones in my LFS and on Amazon, and pretty cheap besides. I had 4 airstones running using typical check valves. Switched to the SMC 695 and immediately 2 stones stopped bubbling. The reason being those two stones were 3 years old and the other 2 that kept working were only a week old.

SMC 695 have very strong valves (you can hear the spring snap sharply back after blowing thru them). It takes lots of airpower to get thru the gate forwards against the spring. Just about nothing is going to flow backwards thru the gate and only a strong air current will flow frontwards. Less bubble making power (it takes some pressure just to hold the spring open), but way safer, it's no contest!

They're under $4 at USP but over $20 each buying them on Amazon, for the same item.
https://www.usplastic.com/catalog/it...x?itemid=24234



https://www.amazon.com/1-40-Hose-Pol...dp/B00K75CMYA/

https://www.amazon.com/1-72-Hose-Nyl...dp/B00K75BD9U/

https://www.amazon.com/2-00-Hose-Pol...dp/B00K759KOK/


I also bought a shelf for $45 72" high to raise the airpumps above the tank from Amazon.

[Autumnsky]

Interesting, didn't really think about how cheap these air valves are made, though have had one stop working in the past year or so and one cracked the end off which connects the air tubing, so that could be a very big problem.

Being these valves are also for liquid it is easy to see how they could be so strong and need a newer pump /one with a newer diaphragm. That is good info to know.

[T Waters]

Yeah I was satisfied with my old checkvalves which allowed all 4 stones to work (all stones were identical make and model, 2 were old and 2 were almost new). The SMC valves have heavy springs and would not bubble the two old stones. Which I think is a very big plus, tells me to replace (or clean) the old stones, meanwhile that heavy spring is just not going to allow anything flowing backwards.


I was surprised when testing showed one of my old valves allowed blowing air thru with my mouth both directions. It wasn't that way when I installed it about 3 years ago. The weak valve had broken down over time.

[Autumnsky]

"...weak valve had broken down over time."

Good point to remind us all to replace or at least check as periodic maintenance. I wouldn't have really thought to do that. Being that I was about to buy a dozen pack of the cheapo bulk purchase valves, I think actually buying the better quality especially for a large tank makes sense.