Portable Restroom Operators Tackle Vacuum Truck Valve & Electrical Issues

The sight of another PRO’s truck rolling down the road has this operator asking some questions.
Portable Restroom Operators Tackle Vacuum Truck Valve & Electrical Issues
This graphic from a reader shows what he views as a questionable location for a knife valve at the top of the vacuum tank.

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QUESTION:

Yesterday I was running my route and saw a competitor’s vacuum truck. I was behind him at the red light. I saw two things I wondered about. First, the suction hose on top of the tank was connected to a valve that looked like a knife gate, then the valve was connected to an elbow welded directly to the tank. I have not seen that type of hook-up.

My first question is: What was the need for that valve hooked directly to an elbow? There is already a banjo valve at the other end of the hose. Please explain. Is this a good idea or not? Just to make sure you understand the setup, I have included a sketch.

Secondly, running down the middle of the tank’s rear head were black electrical wires connected to the rear lights on top of the tank. I’m no expert about electricity, but shouldn’t those wires be hidden or placed somewhere to reduce the chance of shorting?

Hank Cavanaugh

Boise, Idaho

ANSWER:

Good questions. Having a banjo valve at the operational end of the hose and a knife gate or ball valve at the point of connection to the truck is a good idea. In a vacuum truck system, problems can occur at multiple points. One trouble spot is the main suction hose between the operator’s end and where it enters the tank.

If a pumper is on a job and everything is running smoothly, then suddenly the system seems to bog down, the first potential problem might be a blockage in the hose. Users are known to throw just about everything into a portable restroom. If a solid object is sucked into the hose and gets stuck halfway to the tank, the pumper can first try to identify the problem by closing the valve and disconnecting the hose.

With the hose disconnected and the valve reopened, the operator will instantly be able to tell if the problem is a blockage in the hose. With the valve open and the vacuum gauge reading normal, then the blockage is in the hose. If the system does not respond when the valve is open, more diagnostics are required.

In that case, turn to the primary shutoff point, the secondary or the pump itself.

When your system seems to bog down or runs differently than normal, don’t wait to diagnose the problem. It may be as simple as a clogged hose or it might be something more serious that is on the verge of causing damage to your pump. Quick response can save a lot of time and money.

And a side note: Some manufacturers place valves between the primary and the secondary, and then from the secondary to the pump. This simplifies hose removal in the event they are clogged or damaged and need replacement. Typically trucks are set up for easy diagnosis of vacuum system issues.

On to your question regarding the electrical cord running down the rear head. This is not a good idea. A lot of people will claim that the cord is well insulated so it isn’t going to make any difference where the electrical wiring is placed. I can think of reasons why the electrical wiring should not be in that position. An exposed wire can be hooked by the technician or anyone walking past the truck. And there is always the rain. Even the best insulated wiring can short out in the right storm.

Secondly, apparently the contractor rigged the wiring in a hurry, and just wanted to get it plugged in and go to work.

The way to solve both of these wiring issues is to roll a pipe that matches the diameter of the tank and attach it to the rear head. Only a half circle is needed. Then run the wiring through the pipe. When the unit is painted, there is nothing exposed and it looks like a professional rig.



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