SeaMonster's 100 gallon cube

I think Vinny is referring to the line from the sump to the pump in the saltwater holding tank. The pressure of the water in the sump will push back through the pump when it's turned off. You might be able to put a vacuum break in the line sort of like for lawn sprinklers. Or just add a valve

 

Is that "Top Off" valve in the sump or is that a faucet for clean water? The more I look at that line the less sense it makes, why would you have a line from the fresh water able to top off the sump? You would have a line from the RODI to the fresh water tank right?

 

You have to be out with the tank to put in the salt so turn the valve then, come back later when your testing the salt SG and if everything is ok turn the valve back

 

Thanks for the observations.....I have to go stare at the design a bit more..... I plan on testing with tap water
So RODI fills the top FW container, which can supply either the salt water making container, or go straight to top off the sump.
SW or FW can not be syphoned back since their drain sits slightly above water level....the blueprint above is a rough approximation....should have photos of the first draft by Sunday.

 

Is that the water level in the sump with or without the power on? With the power off the level can rise considerably.
When you get the new drawing done with updates please share

 

Showing the water level in the sump helps a lot. Throw away that suggestion I made about a vacuum break, it won't work that way. Now you still have the problem of the flow between the Saltwater holding tank and the sump. Consider a pump as an accelerator NOT a valve

 

Not sure what the problem is. Both fresh and salt water pipes will be above water level with pump off.....maybe need a splash guard of some sort

 

No, the problem is at the pump end in the saltwater storage tank. Even with the pump off and the other end above the sump water level, the saltwater will flow due to gravity and the higher water level in the storage tank. You will need to put a valve somewhere on that line.

 

I see. Thanks for the input. Its actually another flaw in the drawing, the final product does not have this issue. Water has to travel up more than you see in the image

 

You guys know if it is OK to pour SW down a downspout drain? Not sure if that is the name; this is the underground pipe the downspout drains into