Move solids-containing liquids with fewer clogs by understanding trash pumps and what they can—and can’t—do.
Trash pumps are the workhorses of the pumping world. When you need to move a liquid that contains debris or solids, whether it’s pond water sludge, storm debris, mud or sand, a trash pump may be the way to go.
Misunderstandings about trash pumps are common. Here are answers to eight frequently asked questions.
1. What is a trash pump?
A trash pump is a pump designed to transport liquids that contains hard and soft solids such as leaves, twigs, pebbles, silt and mud. Most trash pumps are centrifugal pumps. They may be referred to as wastewater pumps, sewage pumps or sludge pumps, though you’ll need a true sludge pump, not a trash pump, to move a thick fluid with a high solids content.
Trash pumps come in a variety of sizes. Contractors can carry small gas or electric trash pumps from jobsite to jobsite. Trash pumps also come in large, trailer-mounted, diesel-driven models, which are sometimes referred to as tow-behind pumps, standard pumps or industrial trash pumps. Different types of trash pump have different impeller designs to handle specific types and sizes of materials.
Some solids-handling pumps are submersible. Technically, these are called submersible pumps, but they are sometimes referred to as submersible trash pumps.
2. Trash pump vs. water pump: What’s the difference?
Trash pumps are useful when the liquid being pumped contains solids that a water pump can’t handle — and that means any solids, since water pumps are designed to move clear liquids. Water pumps move liquid at higher pressure than trash pumps. But if you try to use a water pump to move murky water or water that contains pebbles or other solids, it will likely jam.
3. What are common trash pump uses?
Trash pumps can be used for any application where you need to move a fluid that contains solids from point A to point B without high pressure. (For high pressure, you’ll need a high head pump.) Applications include:
General site dewatering, such as removing water from drainage ditches
Draining water from a containment
Creek bypass when the water contains leaves, stones or twigs
Sewer bypass projects
4. How does a trash pump work?
A trash pump has a rotating engine that powers a shaft that spins. Attached to the shaft is an impeller. As the impeller spins, the water is collected and pushed through the discharge line. Most trash pumps have an open or semi-open impeller design that lets solids such as rocks pass through. With these impellers, the tradeoff for fewer jams is lower flow efficiency.
5. What size solids can a trash pump handle?
The size of the solids a trash pump can handle depends on the size and model of the pump. The main determining factors are the diameter of the suction and discharge openings and the clearance between the volute and impeller.
6. How far will a trash pump lift water?
A typical centrifugal trash pump will pull suction up to a 25-foot lift, depending on the application. A trailer-mounted trash pump can lift fluids as high as 150 feet.
7. Can you use a trash pump for sewage?
A trash pump of an adequate size is often suitable for sewage sludge removal.If the solids concentration is too high, however — more than 3% or 5%, depending on the pump — it may clog. For larger solids or higher concentrations of solids, you’ll need a sludge pump.
8. How can I choose the best trash pump for my application?
There are several factors to consider when buying or renting a trash pump.
The size of the solids
Know the material you’re pumping. Don’t choose a pump designed for 1-inch solids if you might encounter 2-inch solids. You’ll end up with jams and possibly, pump damage.
The volume of fluid being moved
Understanding the volume you need is critical to sizing a pump. Trash pumps range from 3-inch pumps with a flow rate of 200 gallons per minute (gpm) to 18-inch pumps that can move 10,000 gpm to 11,000 gpm. Keep in mind that volume is limited by your hose size.
The size of your piping
The smaller the hose, the greater the friction loss. Friction loss must be factored into your pump choice to achieve the flow rate you need.
Your preferred power source
Smaller trash pumps are electric or gas. Large trash pumps have traditionally been powered by diesel, but more and more electric models are available today because of cost considerations and sustainability concerns.
Choosing the right trash pump for your application will minimize jams and clogs. When they do occur, cleaning out the impeller is relatively quick and easy.
If you’re renting a pump, the pump experts at United Rentals will ask questions to help you accurately calculate your flow and to get you a pump designed to handle the solids you’re moving efficiently and with minimal downtime.