QUESTION: I recently bought a used vacuum truck to pump restrooms. It wasn't long after I got started with the truck that the pump began getting clogged. The tank has a primary on top and a secondary on the side. I opened the manway on top and took a look inside the tank with a flashlight. All I could see was a 6-inch stainless steel ball on the floor of the tank. What purpose does that serve? Is that ball supposed to block something?
Ray Spence
Wichita, Kan.
ANSWER: That stainless steel ball on the floor of the tank is the main reason your pump is getting clogged. If you'll remove the snap ring or the wing nuts that hold the primary together (depending on the type of primary) and take a look, you'll see the interior parts of the primary have rusted and rotted away. That 6-inch stainless steel ball belongs in the cage of the primary shutoff, not on the floor of the tank.
Stainless steel lasts a long time, while carbon steel rusts and disintegrates in a wet environment. Without the ball in the cage, waste and other contaminants are able to slip through the primary unblocked and go directly to the secondary. The secondary moisture trap is just what it says it is. It is a second chance to catch what the primary missed.
By letting everything pass freely through the primary, it is likely the secondary couldn't catch everything in the path to the pump. Consequently, you've got a damaged pump because someone forgot to check the condition of these two vital parts.
When operating properly with the stainless steel ball in the cage of the primary, the ball will rise as the load enters and fills the tank. When the tank is close to reaching capacity, the ball will stop any debris or waste from flowing through the system. Hopefully, what little waste that does manage to escape goes to the secondary and is stopped there.
Always remember the primary shutoff and the secondary moisture trap are the parts designed to save your pump from damage. The pump is your lifeblood for the system.
So how often do you need to check the primary shutoff and the secondary moisture trap? Clearly, in your case the primary had not been checked for months and maybe years. Pumpers often forget to climb up on the tank and undo the lid of the primary. I wouldn't be surprised that the vanes in the pump also are damaged, requiring replacement of the vanes, gaskets and bearings. So let's review the recommended inspections of these parts:
Check the primary shutoff monthly.
Check for the amount of rust and, obviously, make sure the stainless steel ball is in the cage. Everything needs to be in pretty good shape. You might find some rust, but that doesn't mean the primary is about to fail.
Empty the secondary daily.
After a day of pumping, the secondary must be emptied before the next day of work. It's even better to empty it upon arriving back in your shop. By waiting overnight to empty it, two bad things can happen.
First, in cold weather, the waste freezes, limiting the effectiveness of the primary because the waste won't drain easily. You might think only small amounts are trapped in the secondary, but as the system warms up and the material loosens, your pump will pay the price and you will pay the repair bill.
Second, upon arriving at work it's easy to assume the secondary is empty or someone simply forgot to drain it. In which case you're back to a damaged pump.
TEAR IT DOWN
If you are unfamiliar with how these parts look and function, take them apart. Check the condition of your primary and see how the secondary functions in much the same manner except it has an area to catch debris. The primary will essentially shut off the system while the secondary catches waste that passes through. When these two accessories are checked and working properly, your pump will hum along.
