Question:
Lately, whenever I get done pumping, I turn off my vacuum pump and it starts spinning backwards. Is something broke? Makes me wonder if I need a new vacuum pump. But when I turn the pump on again, it runs pretty much OK. Tell me anything, but don’t tell me I need a new pump.
Roger McClansky
Pierre, S.D.
Answer:
If you want to buy a new pump, you can, but it really isn’t necessary. This question comes up quite a bit at seminars. So don’t think you’re the only one with this problem. It happens. Here’s what’s going on.
If you have a pump with a four-way valve, the flap under the valve is bad or gone. This can be repaired by replacing the flap. Make sure you look at your parts manual to get the right part for the right pump. Not all parts are interchangeable for different pumps. What happens when this flap breaks, or in some cases just disappears, is that you turn off your vacuum pump, and with the flap broken or gone, the vacuum now wants to escape, if possible. This flap makes it possible.
In the event you don’t have a four-way valve, look into the check valve. When there is no four-way valve on the pump, a check valve inside the pump holds the vacuum when the pump is turned off. This valve, if broken, will need to be replaced.
What’s the point of all these manways anyway?
Question:
I haven’t been in the business long, but I have a question about manways. My tank has an 1,100-gallon capacity, but no manway on top. It does have one coming out the rear head. I’ve seen lots of trucks with manways on top and no manway in the back. What exactly is the purpose, if there is one, for these manways? And if I buy another tank, do I really need any manways?
Norm Merriman
Portland, Ore.
Answer:
First, your tank does not require any manways for the system to function properly. There are three main reasons why pumpers have manholes in their tanks:
• First, the manway on top provides access for visual inspection of the inside of the tank. Sometimes a pumper may need to check the condition of his baffles inside the tank or look for other defects in the tank. And it’s handy for cleaning out the tank with a hose, if needed. This cleaning can be done from above when some items are not dumping. Water pressure can sometimes free up sticky stuff. This is especially helpful in cleaning out the front part of the tank, which can’t be reached from the rear.
The downside to manways on top of the tank is that they add an element of risk for those climbing up to open the lid. A man can slide or fall off the tank and possibly get hurt, so care needs to be taken to avoid accidents and injury.
• Second, the rear manway allows for cleaning also. With the rear hatch open, one can again hose out the rear section of the tank. This can be done on the ground and allows for easier and more complete dumping. But, as mentioned above, it may not reach up into the front of the tank if there are baffles in the tank.
• Third, and this is the one that nobody likes, manways on top and in the rear provide access for someone to get inside the tank if necessary. Nobody wants to, but there are times that repairs must be made from the inside. If there are no manways in the tank and the tank needs repair, you will soon be paying for a manhole because the only way to get inside the tank is to cut a hole and put a manway in the place of the cut. It is true, however, that it is possible you’ll never open up a manway on top of the tank.
Most of the people we deal with put one on top of their tank. Not everybody puts a manway out the rear head. It’s a good idea, but if you have a history of pumping stuff that flows easily, then there is no real need for the rear manhole. Many people simply go with a 4-inch or 6-inch dump valve. Again, it depends on what you are pumping. It adds to the cost of a tank to add these manways, so if you don’t really need them, save your money.
