Over or Under

When using jet siphon devices to transfer water between dump tanks during water shuttles, the question of where to secure the discharge ends of the jet siphon tubes seems to bring a mixed response.  Should they be secured over or under the water? Here is a brief perspective on their placement. 

 

I believe that securing them over the tank rail and above the water line is the most advantageous option.  This placement provides the following advantages;

• The hard sleeve does not have to be as long to drape between both tanks.
• The open end of the tube is visible so that the quality of the water flow is easily identifiable.
• The operator(s) of the jet siphons can determine which ones are flowing
• The water being discharged does not push strainers on the bottom of the tanks around
• When tanks are on a slope, having the discharge end above the water line is ideal so that when the jet is shut off, water will not flow backwards - in a reverse siphon.  This can accidentally drain water from the main tank if it isn't attended to.

On the con side, having the ends of the tubes at the tank rail requires they be secured.  Rope, webbing or bungee straps all work.  For speed, heavy duty bungee cords or lightweight ratchet belts are worth considering.  The air that's entrained into the dump tank by the discharge of the jet siphon above the water line into the receiving tank has not shown any notable negative impact at any operation I have been involved with. 

 

The quality of water flowing from the far siphon shows air is entrained.  From a distance this tells us the tank level is low and we can expect that this device has or will shorty stop transferring water.

The more laminar looking flow of this siphon shows us that it is operating properly, and is not drawing any air in.  With its discharge end above the rail we can tell its obviously working as expected.

In this 2200 GPM water shuttle, it helps to see the ends of the siphon tubes to know that the flow can be maintained.  in High volume water shuttles, surprises are not good, so being able to monitor each siphon tubes flow is very important.

 

Webbing, rope, or bungee straps can be used to secure the tunes to tank rails. 

 

In this photo, you cannot tell which of the 7 jet siphons is flowing, nor can you tell the quality of water flowing form them.  This operation supported 2500+ GPM, but had two separate control locations for jet siphons.  If the control operators could see the ends of each tube it would make coordination a bit easier.

 

You can see the far siphon indicating flow is lost in the dump tank, as air is entrained.  The near siphon is delivering a significant volume of water still

 

This 2600 GPM water shuttle had siphons above and below the water. 

With regard to jet siphons, a few other things to remember are;

• Pump the siphons at no less than 100 PSI.  125-150 PSI is ideal.
• Provide a dedicated water transfer engine at the dump site, so that total capacity from the supply pumper to the fire is not stolen to "drive" the jet siphons.
• There are many brands of jet siphons with different performances.  Check out an article we did on jet siphon flows;
• http://send-the-water.blogspot.com/2013/10/water-transfer-testing-jet-siphon-flow.html
• Here is an article by GBW Associates at http://www.gotbigwater.com/content/data/file/Jet%20Siphon%20Flowtests.pdf

In conclusion, securing the jet siphon tubes above the tank rail provides several advantages over placing them under the water.  If you haven't already, try it out next time you drill.