Rural Water Supply

Over or Under

Placement of Jet Siphon Tubes

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.

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.

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.

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. If you are supervising the operation, can you tell which ones are working?

The site supervisor can tell a lot by this photo, including to radio up to the delivery end of the operation that the water supply is nearing an interruption. The entrained air and poor quality of the jet siphon tells him that the second tank is empty. In this instance, he requested one ladder pipe to be shut down during several periods where water in the tanks ran low.

This is a best case scenario. Two jet sipons discharging high volumes of water, and tanks filled to the brim.

Using a gated wye or manifold allows an attendant to sit back and control jet siphon use from a distance. This is another reason it is best to keep the siphons above the rail

Pump it or Dump It?

Nursing vs. Dumping for Water Supply

Don't Send The Water!?

How Much are Those Last Few Gallons Really Worth?

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