This feature in Pumper reports noteworthy conversations that take place at the Pumper Discussion Forum, an online forum for industry professionals found at www.pumper.com. Pumper Discussion enables exchange of information and ideas on septic and drainfield installation and maintenance, trucks and equipment, portable sanitation, chemical and additives and much more. Information and advice in “Overheard Online” is offered in good faith by industry professionals. However, readers should consult in depth with appropriate industry sources before applying such advice to a specific business situation.

Question:

The graphic shows my current vacuum truck setup. I’m having an issue with sand, silt and gravel building up in the bottom of the tank. The debris runs on a gradual incline (higher to the front). I have installed a 12-inch manway in the rear of the tank and have made a 10-foot-long handled scraper to drag the sand back (similar to a catch basin spoon), but it doesn’t really work well and makes a big mess. Blasting with a pressure washer from the top manways won’t budge the sand.

Are there ways I can modify my current tank to keep it clean? Different valve and vent locations? We have to discharge through a 4-inch hose at our treatment plant. I pump and discharge from the same 4-inch rear valve, and when I unload at the plant I open a 2-inch ball valve at the top rear of the tank. I have been thinking of putting a 3-inch valve on the bottom front end of the tank and pumping every few tanks through that. Would that help?

Should my air vent be in the front rather than the rear for unloading? Is 2 inches too small?

I don’t have a hoist. I drive the truck onto ramps on the front end to raise it a foot, but that doesn’t really work as well as I had hoped. My tank will hold 850 gallons of waste, but with the sand and sediment I lose about 100 gallons of capacity.

ANSWERS:

Have you considered adding a load port at the front of the tank, possibly with a 90-degree elbow off the tank and extension pipe so your hose connection is at the side of the truck? Then switch from rear- to front-loading every so often.

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I have the same problem. My truck has a hoist that tips to 50 degrees and the silt/sand still sticks in the front. I have added a vibrator, which is bolted to the bottom of the tank, and I activate it for a few seconds as I unload. This helps quite a bit, but I still wash my tank out every couple of months.

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I have thrown a jetter in there and it pulls that stuff out real well.

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I have a 2-inch water pump with pipe fittings reducing down to a 3/4-inch pipe nipple for a nozzle. I can wash the grit out pretty quickly from the topside manway.

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I have a long length of 3/8-inch pipe with a welded plate made to the contour of the tank. I have two 1/4-inch holes drilled about 15 degrees from center of bottom, then I have a garden hose adapter on the end. I graded a pile of dirt and created a ramp. I drive up the ramp, open the hatch, turn the water on and start raking. It takes a little effort and time but gets the job done.

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My trucks have 6-inch outlets that exit from the bottom of the tank. A couple of interior baffles have half-moon openings right on the bottom of the tank, which does a great job of drawing the contents out of the tank with enough force to take the sediment with it. If you have to dump using a 4-inch outlet, your tank is not going to stay clean. The plant operators know this. They don’t want your gravel and stones. They make more money, because you can’t dump a full truckload.