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Fluid Engineer Explanation Please-inverted P-trap


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So I have 2 opened top 1000 L water tanks with the drains combining feeding into a pump, that recirculates the water through a filter back to the tank water inlets. A water flow fault caused one tank to partially empty and one tank to overflow.

Evidently I can fix the problem of a tank overflowing by installing in the tank drains an inverted P-trap at the height I want the tank water level to maintain at.

So 2 tanks and 2 inverted P- traps.

What's the theory of how this works? Why does the level in the P-trap stay at the same level as the height of the water in the tank?

 

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You have the physics correct.    Too much flow is the amount that will cause the air in the down pipe to be sucked into the outflow. This will change an overflow system to become an auto-siphon

So you are going to common together the tank overflows and then have the "real" overflow outlet at a slightly higher level?   Each tank will overflow into the other but if the level rises ab

How about a sketch showing the system layout. 

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5 minutes ago, carlyai said:

So I have 2 opened top 1000 L water tanks with the drains combining feeding into a pump, that recirculates the water through a filter back to the tank water inlets. A water flow fault caused one tank to partially empty and one tank to overflow.

Evidently I can fix the problem of a tank overflowing by installing in the tank drains an inverted P-trap at the height I want the tank water level to maintain at.

So 2 tanks and 2 inverted P- traps.

What's the theory of how this works? Why does the level in the P-trap stay at the same level as the height of the water in the tank?

 

That doesn’t sound as if there’s enough information on the structure of the piping and where the outflow of the traps are going. It also sounds as if, depending on the size of the pipe in the trap, you could accidentally create an auto-siphon, and I don’t think that is what’s intended 

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So you are going to common together the tank overflows and then have the "real" overflow outlet at a slightly higher level?

 

Each tank will overflow into the other but if the level rises above the outlet then both tanks overflow simultaneously to drain?

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There is one of these P-trap builds for each tank and the top open end of the P- traps go to a common pipe to the pump which pumps the water through a filter back to the tanks.

I really want to know how this works.

I think it keeps the level of water of the fish tank to the same level as in the P-trap, so if the P-trap is below the level of the top of the tank the tank shouldn't overflow. 

But if one tank had a blockage in it's drain but was still having water pumped to it, it would still overflow regardless of the P-trap.

So it would probably be better off having 2 float switches so that the pump would be cut off before the tank overflowed.

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Can you sketch out (or use the construction drawings) what you have with some sense of height and scale.

 

A couple of floats and some relays would certainly be handy as an overflow backup.

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Think I've got a vid of my system now. Already a couple of mods coming for the sump.

Would just like to know why/how the inverted P trap will stop overflows.

I think I understand how the tank water level will be the same level as the P-trap. So if the P trap is lower than the top of the tank the water will not overflow from the tank.

But if something gets stuck in 1 tank drain or and water is still filling that tank it is still going to overflow.

I'll buy a couple more of those orange tank float pump cutout switches that you and sometimewoodworker put me onto.

We got a bag of fish from the local Mekong river hatchery. I wanted 60 all male tilapia of a reasonable size. No can do. So got a mixed bag of everything. Some of the fish were too small and got sucked into the drain causing one tank to keep filling and the other not to fill, so 2000 L into a 1000 L tank don't work.

Modifying the drain cover so small fish can't get sucked in to the drain pipes. Then modified P trap and pump cutout. Should be right to wind it up again.

 

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Unless the inflow is huge, it looks as if the only benefit of the inverted P is to keep junk from blocking the overflow. That is assuming that what you showed is all there is.

 

certainly a couple of  float switches can be set to cut off the pump if the level in either/both tanks goes too high & it’s not rocket science to design the circuit.

 

you may be able to use mosquito net and a jubilee clip as a fry protection filter 

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sometimewoodworker wrote 'Unless the inflow is huge, it looks as if the only benefit of the inverted P is to keep junk from blocking the overflow. That is assuming that what you showed is all there is.'

Am I right in assuming that the height I set the P trap to will be the height of the water in the tank?

 

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5 hours ago, VocalNeal said:

So you are going to common together the tank overflows and then have the "real" overflow outlet at a slightly higher level?

 

Each tank will overflow into the other but if the level rises above the outlet then both tanks overflow simultaneously to drain?

My setup vid. Later will just be changed to connect the P traps in the sump pipes if needed. I'm not sure I need them if I have float switch pump cutouts in the tanks.

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Be careful linking your "traps", you may inadvertently create a syphon which would drain the tank if it overflows, I assume your fish wouldn't like that.

 

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1 hour ago, Crossy said:

Be careful linking your "traps", you may inadvertently create a syphon which would drain the tank if it overflows, I assume your fish wouldn't like that.

 

 

Not if the first verticle elbow is a Tee?

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10 hours ago, Artisi said:

How about a sketch showing the system layout. 

I posted a video of the layout. Not good enough? 

The only difference to the layout in the video will be that both the drain pipes exit the bottom of the tanks then ascend vertically to the inverted P-traps (set at a level about 1000 mark) then descend to join the drain pipe.

The other pipe setup is the same.

Another modification will be in the sum to change the sump covers as they are hard plastic and warped during heating and don't deal properly.

 

So setup looks like vid but P-traps added.

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Soooo the way I see it is that the level of water in the bottom of the P-trap will be at the same height as the water level in the tank. (Must be someone's law.)

Without any pipe blockages, if the water flowing into one tank is more than the water flowing into the other tank the tank won't overflow as it will only reach the level of the P-trap and the drain will drain more, so tanks won't overflow. 

That's my main premise.

Stopping pipe/pump blockages due to small fish being sucked into the drains will be completed with drain cover modification and sourcing correct fishlings.

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