Can I pump from one truck to another?
Question:
I have a 3,500-gallon vacuum truck and a 1,500-gallon vacuum truck. I always fill the big truck to go and dump. Can I pump straight out of the outlet on the small truck right into the big truck without hurting the pump or anything else on the trucks? I’ve been dumping the small truck into a holding tank and then pumping out the holding tank with the big truck, but it just takes extra time and work.
Answers:
It’s no problem, as long as you put your small truck’s vacuum pump in neutral so it can draw air. Be sure your secondary and/or your oil catch muffler are not loaded up. You can suck it out or blow it out. You can even do both.
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You can suck right out of the small truck, but open a manway or something. You could also pressurize the small truck and move the material into the larger truck. Again, open the manway when doing so.
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I do this all the time and it works well. I first connect the big truck where I normally connect to pump septic tanks via a 3-inch hose to the outlet on the small truck. I open the drain valve on my little truck, which allows air into the smaller tank. I open up the 3-inch lever valve on the small truck first. I then start the big truck and put it on the vacuum side. After I get around 5-10-inches of vacuum, I open the gate valve on my big truck, sucking anything out of the smaller truck. When the small truck is pumped out, I close the valve on the big truck, then open the secondary drain valve on the big truck to equalize the pressure. Then I disconnect from the big truck. I put the hose against the little truck so no waste drains out. There is always some in the hose. I then close all the valves on the little truck to create some vacuum. This sucks what is left in the hose back into the little truck. I then close the valve, shut the truck off and put away the hose. The whole process takes about 10 minutes.
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How do you tell when the smaller truck is empty if it doesn’t have sight glasses or any means of determining load level? We always vacuum till the primary shuts off.
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The hose connecting the two trucks will be much lighter (as an empty hose would feel). Also, when you get down toward the end, the hose will jump around a lot. Usually, when it stops jumping, it’s empty. Be careful that you are not just plugged up. Check to be sure that air is drawing in through your pump exhaust.
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I’d be worried. Without sight glasses, how do you tell how much is in the little truck to start with? Trusting the overfill protection isn’t a great idea, as all shutoffs are there to protect the pump, not to tell you that the tank is full. We charge an hourly rate, plus volume, and sight glasses are positive proof to both operator and customer in regard to volume removed.
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Sight glasses are OK, but in-between-glass-guessing can reduce credibility. The last truck we had built has no glasses installed. We have a sight tube on the front of the tank. We used a water meter to fill and marked off every 500 gallons on the tube. We also made a provision to install a digital gauge if the tube did not work out. Our second truck has the float hooked to a digital meter. I don’t think I would build another truck with sight glasses. On the first truck, we were always removing and cleaning the sight glasses. We did find that if you clean them and apply a good coat of car wax, they would stay cleaner longer. Also a sight tube goes all the way from the top to the bottom of the tank, can be shut off at both ends and has cleanout caps to clean the tube without removal.
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Some of our customers will have us install the 2-inch sight tube starting at 500 gallons. This will help keep the sand and sludge from getting into or blocking the tube. As far as freezing, I am sure it’s possible and I am sure they have frozen. However, I have not heard of any negative reports back through all the years we have installed them. Don’t get me wrong; I don’t push any specific level indicator. We install all types. If you were to consider a 2-inch sight tube, ask about or request ball valve shutoffs on both top and bottom. They are not part of a standard kit.
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I use 2-inch food grade hose on my truck. If it freezes, it bows out a little but doesn’t break. On my old truck, I had a rigid sight tube that would freeze and break. When designing the sight tube, make sure that when you empty your truck, it is designed to drain empty. Mine comes off the side pointing down, then an elbow pointing up to hook a hose on. It doesn’t drain, but my truck is in a heated shop every night so it thaws. Also mount the tube on the back of the truck so wind doesn’t freeze it quicker.
