Are You Heading for Tank Trouble?

Premature pump failures, costly collapses and dangerous explosions. Oh my! Let’s review basic vacuum truck add-ons to prevent these disasters.
Are You Heading for Tank Trouble?
It’s simple. Knowing the parts and understanding your system will lead to increased truck profitability.

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A vacuum tank will hold vacuum without all the accessories. You can hook up a vacuum pump to a vacuum tank, evacuate the tank, and have yourself a strong vacuum. Without the accessories, however, it is very likely that the tank will collapse because there is no control over how much vacuum is being created.

With too much vacuum, the longitudinal walls (the straight shell) of the tank will collapse. If you can live with a collapsed tank, then you’re all set. So rather than try to identify parts that are or are not necessary in your vacuum tank, let’s first identify the parts in the typical vacuum tank, determine their purpose, and then decide if they are necessary.

Here are six parts that might be considered “accessories,” and a brief description of what they do: 

1. The primary shut-off

Located in the top of the tank, the primary shut-off blocks waste and debris from leaving the tank as the tank fills.

A stainless steel ball, acting as a float, will rise and block the passage out of the tank when the tank becomes full. This prevents waste and debris from entering the pump. 

2. Secondary moisture trap

Located on the outside of the vacuum tank, the secondary is the second line of defense in protecting your pump from waste. If waste passes through the primary — and some will — it is trapped in the secondary. The secondary should be drained at the end of every workday.

One common, costly mistake is to let the truck sit overnight and then forget to drain the secondary. What happens? The vacuum pump is turned on and waste that has been sitting in the secondary flows directly into the pump. Whoops! 

3. Oil catch muffler

As the pump runs, excess oil is thrown off and caught by the oil catch muffler. Pretty simple. Rather than throw the excess oil all over the place, the oil catch muffler saves it and quiets the pump at the same time. 

Like the secondary, the oil catch muffler should be drained every day. The pump will run just fine without an oil catch muffler, but your local and federal environmental protection officials might be all over you for operating without one. 

4. Vacuum relief valve

The vacuum relief valve does exactly what its name implies. When the vacuum in the tank reaches a certain level, the vacuum relief valve opens and gives relief to the tank in the form of outside air. 

By controlling the vacuum inside the tank, you can avoid the embarrassing moment of having the tank collapse. Generally, a vacuum relief valve is set around 20 inches of mercury. 

5. Pressure relief valve

The pressure relief valve is the opposite of the vacuum relief valve. When the tank is pressurized for unloading, the pressure relief valve kicks in when the pressure inside the tank becomes too high, thus avoiding a tank explosion. The valve opens up and pressure inside the tank is allowed to vent to the outside atmosphere. 

6. Pressure/vacuum gauge

This simple gauge measures the pressure or the vacuum inside the tank. It allows the operator to visually inspect how well the pump is working and provides a quick, easy way to determine if the vacuum and pressure relief valves are in good working order. 

It also serves to show you how well the system is working. For example, you’ve been running your truck for several months and it pulls 20 inches of mercury in just a few minutes. Day after day you have been getting the same basic operation. Then one day it only builds up to 15 inches of mercury. With the gauge, you’ll know something is going wrong with the system right away. 

There you have it. These are the basic accessories to a vacuum truck. The primary and secondary are designed to protect the pump. The oil catch muffler protects you and the environment. The pressure and vacuum relief valves protect the life of your tank. And lastly, the pressure/vacuum gauge monitors the health of your vacuum system.

It’s simple. Knowing the parts and understanding your system will lead to increased truck profitability.

Get the most out of your vacuum truck with these cherry-picked pumps:

  • The PV750 rotary vane pump from Presvac Systems is designed for continuous full vacuum operation in extreme conditions.
  • The VK650 fan-cooled vacuum/pressure pump from Masport features an integrated inlet filter that includes a washable stainless steel filter for long filter life.
  • The Eliminator 250 vacuum pump package from Fruitland Manufacturing is specifically designed for the portable sanitation service industry, and includes an RCF250 commercial and continuous duty vacuum pump that creates 180 cfm.
  • The PM60A air-cooled vacuum pump from Moro USA weighs 265 pounds, has 29 psi positive pressure capability, 198 cfm free airflow at 1,100 rpm, and a suggested tank size between 500 to 2,500 gallons.
  • The 4307 Challenger Series tri-lobe blower package from National Vacuum Equipment includes a 535 cfm blower that can generate 26 to 27 inches Hg of continuous vacuum power, depending on working conditions.
  • Conde Powerpak preassembled, gasoline- or diesel-powered vacuum pump units from Westmoor Ltd. are installed by simply bolting them down and attaching them to the tank.
  • The Jurop R260 vacuum pump from Jurop/Chandler requires an input of 540 to 1,000 rpm and creates an output of 363 cfm at free air (304 cfm at 18 inches Hg), while producing a maximum pressure of 25 psi and maintaining 92 percent vacuum efficiency.
  • Emperor Pump KFZ Series aggressive environment pumps from Water Cannon are rated up to 112 gpm at pressures up to 21,750 psi.

For complete product listings and manufacturer contact information, visit

Bob Carlson is author of Pumper 101: The Complete Guide to Owning and Operating a Vacuum Truck and has spent many years building and repairing trucks for the portable sanitation industry.


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