Flow Testing

As previously stated under “Vent Design”, the vent is designed with better than a 2:1 air intake ratio. With this intake ratio, from a design standpoint, the vent should cause no restriction. This said however other factors often come into play.

If after testing your underground tank installation for maximum flow you experience a lower flow than expected, here are a few suggestions you can try.

Preparations for Trouble Shooting:

First - review the designed flow calculations of the Tank System. If you do not have these calculations, you may obtain them free of charge from ETT, L.L.C. by calling or faxing your information to toll free 877-827-2797. Upon obtaining this information compare it to your flow results. In analyzing this data also take into account information contained in the notes below:

Note 1: In an underground tank installation lift will increase quickly as the water level drops. You may see a substantial swing in flow rate as the lift increases. The highest flow rate will occur when the tank is full and flow will diminish as the water level drops. The larger the tank diameter or the deeper a tank is buried, the greater this drop may be noticed, as you will be lifting water higher and higher.

Note 2: Engines with pumps having worn packing or leaking valves, may experience pump cavitation or some loss of flow as lift increases. Each installation should be fully tested with all potentially “responding” pieces of equipment to see if this is an issue or not. If it is, repairs to pump or valves on this equipment may be required.

Note 3: ISO only recognizes installations with lift of 15 feet or less. For a tank installation this would be the vertical dimension from the intake of the pump to the bottom suction point in the tank. Generally this will not be an issue but installations at high sea levels may experience problems.

Second – Make a list of facts you observe. What was the;

  1. Suction Hose Size & Length? How much “dry” pipe do you have?
  2. What was your priming time?
  3. Which suction intake were you drafting from? Front – Side – Rear?
  4. Pump Size – What stage (volume or pressure) were you drafting in?
  5. What is your pump Capacity?
  6. What outlet were you discharging from?
  7. What type of discharge was used? Deck Gun, Portable Deluge & what size tip?
  8. If hose lay was used, number of lines, diameter, length what kind & size of tip?
  9. Did you check for kinks in the discharge lines?
  10. Was you flow steady or did it diminish as time went on?
  11. Did you observe any leaks – air or water?
  12. Was the flow intermittent? Did you observe air in the stream flow?
  13. Was your on-board tank still full? Did you your pump to tank valve open?
  14. Were you re-circulating any water back thru you pump from your tank?
  15. Was your pump by-pass valve set properly? (closed?)
  16. Do you see an increase when flowing from both on-board & suction supply?
  17. Did you have any foam in your tank or have you been using foam recently?
  18. What makes you suspicious of the flow rate? Do you have previous flow data?
  19. Have you tested using other engines? Were the results the same or different?
  20. What was your starting lift? Distance of water surface to center of pump?
  21. What was your ending lift? “ “ “
  22. What is the sea level of you test installation?
  23. Were you refilling the tank as you were drafting?

By answering these questions you will usually be able to self diagnose the issue yourself. If not here are some additional trouble shooting checks that may help.

Trouble Shooting Checks:

1. Verify pump tightness

If air leaks exist, flow could be prevented or diminished, especially as lift increases. The following procedure will tell you if your pump and plumbing are tight.

  1. Remove the large chrome steamer cap from pump.
  2. Attach suction hose to pump.
  3. Remove gasket from inside of the chrome steamer cap and then place the gasket on the back side of the cap.
  4. Hold cap & gasket against the end of the hose and pull the primer. Once maximum vacuum has been reached shut off the primer.
  5. Cap should stay in place for at least 5 minutes. If it falls off quickly there is a leak in the pump system. It could be pump packing, a leaking valve or a leaking hose.
  6. Most of the time, leaks can be found by mixing up a soapy water solution and placing it into a spray bottle. While under vacuum, spray a heavy coating of the solution on all suspected areas. If you see the solution being sucked into the opening, it is a leak.

Note: This procedure checks the suction hose, pump and plumbing.

2. Verify the Vent is in proper working order

Assuming the pump is tight, the following can be done to see if the Tank Vent is causing any constraint.

  1. Remove the 4 bolts holding the bonnet in place and very gently lift the bonnet “vertically” off of the assembly. Make note of the alignment mark. Once removed, inspect the vent holes in the bonnet for blockage.
    If the tank is full, the Red/Green cylinder should have jumped up above the end of the sight glass. Press down on the top of the float rod to see if it floats freely. The Red/Green cylinder should bob up and down, if the float is free.
  2. Next, vertically lift & remove both the float and guide rod assembly. A slight twisting back and forth of the black guides (they look like a wagon wheels) may be necessary, if it is tight. Take care in removing the assembly to prevent bending of the rod. Inspect this assembly for any obstruction such as plastic bags or rags, which could have been left inside the tank during the installation.
  3. If the float rod is bent, causing it to hang up inside the guide rod, gently straighten the rod prior to re-insertion. It should slide freely.
  4. Rerun the test the with all components removed. You now have an unobstructed 8" airway. Compare this test data against that previously observed. You should not see any difference in flow but if you do, inspect the lower cage to see if plastic bags or rags are obstructing the elongated slots near the bottom of the pipe. It will probably be necessary to shine a flash light down inside the vent pipe to inspect for possible blockage. If blockage is present clear as required and retest. If test results are still not satisfactory continue to the next step, leaving the float assembly out for the present time.

3. Verify you have no restrictions in the Suction Supply line

  1. Verify clearance from end of the vertical suction pipe to bottom of tank does not restrict the flow. Clearance around the pipe should be about 54 sq inches. If this distance is very close it could cause a restriction. To verify this may require removal of the water for visual inspection via a man-way or use of a special video camera. Caution: If entry into the tank is required, use all necessary life safety steps as required for a confined space entry.
  2. Verify there are no foreign objects like a rag, plastic bag or paper towel being sucked up against the strainer plate of Dry Hydrant head. Simply remove the SST E'ring, remove the strainer and retest. If a transparent hose is used, check for objects inside the hose, which will now be pulled up to the pump strainer plate. If a rigid solid black suction hose is used, shut pump down and very slowly let the water drain out using the pump drain. Keep the hose bent down low to the ground. Slowly break the seal to the dry hydrant and allow the water to recede out of the hose. Remove hose and check for foreign material.
  3. If the old ridged black suction hose is used, check for internal wall collapse.

    This can be done by:
    1. Connecting the hose to the truck.
    2. Turn on a small flash light and place it inside hose, pointing the light beam up the hose toward the pump.
    3. Using a thick piece of clear Plexiglas and a spare gasket, place it on the end of the hose.
    4. Pull prime and look inside for wall collapse.
      Note: if this cannot easily be done, swap hose and run the pump test with a different hose.
  4. Was the test being performed using a front suction or while discharging from top mounted deck gun.
    Plumbing for either of these, almost without exception, will not yield good results. Plumbing to these points is usually reduced and has several bends and turns. Pump test should be run from a deluge gun located on the ground using 3 to 4 (2 ½” or 3”) lines and a large straight bore nozzle.
  5. If flow is still undesirable review the Dry Hydrant plumbing configuration. Does the installation have internal strainers, bends in the plumbing, any restrictions or reductions and what is the head size and suction hose size.

If none of my suggestions have helped and you still have problems please don't hesitate to call me. Stan Merrett Ph or Fax (toll free) 877-827-2797

(Reinstall the bonnet, float & guide assy after all test have been performed.)