Publish Time: 2026-01-13 Origin: Site
You turn on the tap, expecting a steady stream of water, but instead, you are met with aggressive sputtering, coughing noises, and an uneven flow. In severe cases, the water might stop flowing altogether. This is the classic sign of air entering your pumping system.
For many well owners and industrial operators, the concept seems confusing. If a submersed water pump is completely underwater, how on earth does air get inside it?
It sounds like a paradox, but air entrainment is a common issue that can lead to significant mechanical damage, reduced efficiency, and eventual pump failure. Whether you are managing agricultural irrigation or a residential well, understanding the physics behind this problem is the first step to fixing it.
This guide explores the specific ways air infiltrates submersible systems, how to diagnose the issue, and why upgrading to high-quality stainless steel water pumps might be the long-term solution you need.
To understand the problem, we must first look at how the equipment operates. A submersible pump is a unit that combines a pump and a motor, hermetically sealed and designed to push water to the surface rather than pulling it.
Because they push water, they are generally more efficient than jet pumps. However, they rely on a sealed environment to maintain pressure. When air enters this environment, it disrupts the hydraulic balance. Air is compressible, whereas water is not. When the impeller hits an air pocket, it loses resistance, causing the impeller to spin rapidly without moving liquid. This leads to "air locking" or cavitation damage.
So, how does the air get there? It usually comes down to one of four culprits: low water levels, cascading water, gaseous aquifers, or mechanical leaks.
The most common cause of air intake is a water level that drops too close to the pump intake.
When a pump is active, it creates a "cone of depression" in the water table around the well. If the pumping rate exceeds the well's recharge rate, the water level drops. If the water level falls below the pump intake, the pump will obviously suck in air.
However, air can enter even if the pump is still slightly submerged. If the water level is just a few feet above the intake, the suction can create a vortex—similar to a miniature tornado or the swirl you see when a bathtub drains. This vortex stretches from the surface down to the intake, funneling air directly into the system.
In some wells, water enters from the aquifer at a level higher than the pump. This creates a waterfall effect inside the well casing, known as cascading water.
As the water falls and splashes onto the water surface below, it aerates the water, trapping air bubbles. If your submersed water pump is installed too close to this agitation zone, it will draw in this aerated water. Over time, these bubbles accumulate in the system, causing sputtering at the surface.
Sometimes, the air isn't coming from the surface; it’s coming from the ground. Some aquifers naturally contain high levels of dissolved gases like carbon dioxide, methane, or hydrogen sulfide.
Under the high pressure of the deep aquifer, these gases remain dissolved in the water (much like carbon dioxide in a sealed soda bottle). However, as the pump draws the water up and the pressure decreases, these gases come out of the solution and form bubbles. This is often difficult to fix mechanically, as it is an environmental issue, but gas separators can help.
Air doesn't always enter through the pump intake. Sometimes, it enters through the plumbing above the pump.
Your drop pipe contains a check valve that holds a column of water in the pipe when the pump turns off. If there is a crack in the pipe or a failed check valve, water will drain back down into the well when the pump is idle. This creates a vacuum in the top of the pipe, which pulls air in through faucets or loose fittings at the surface. When the pump turns on again, it pushes this slug of air out of the line, resulting in that violent burst of sputtering.
Diagnosing a pump issue can be tricky. Use the table below to determine if air is your primary problem.
Symptom |
Potential Cause |
Suggested Action |
|---|---|---|
Sputtering water at the faucet |
Air entrainment or gaseous water |
Check water levels; install a gas separator. |
Pump runs but moves no water |
Air lock |
The pump is likely "air bound." Turn it off, let air rise, and restart. Check for drawdown. |
Cloudy/Milky water that clears up |
Dissolved gas release |
Let water sit in a glass. If it clears from bottom to top, it is trapped air/gas. |
Loud hammering noise |
Water hammer (caused by air pockets) |
Inspect check valves and install an air relief valve. |
Rapid cycling (On/Off) |
Waterlogged pressure tank |
The tank has lost its air cushion (opposite problem), or the check valve has failed. |
While environmental factors like water tables are hard to control, mechanical failures are often preventable. Corrosion is a leading cause of holes in pump casings and drop pipes, which subsequently allow air to enter the system.
This is where investing in the best water submersible pump materials matters. Many cheaper pumps use cast iron or lower-grade plastics that degrade over time, especially in acidic groundwater.
Leading manufacturers like Guangdong Ruirong Pump Industry Co., Ltd. prioritize durability by manufacturing stainless steel water pumps. Ruirong utilizes AISI 304 and 316L stainless steel for their motors and pump casings.
Why Stainless Steel?
Corrosion Resistance: It resists rust and oxidation, preventing the formation of pinhole leaks that introduce air.
Seal Integrity: High-quality machining ensures that seals remain tight, preventing air infiltration at connection points.
Longevity: A pump that maintains its structural integrity keeps the system pressurized correctly, reducing the risk of vacuum-related air intake.
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If you have confirmed air is in the system, here are the steps to remediate the issue:
Install a Flow Sleeve: If the issue is a top-feeding well or cascading water, a flow sleeve forces water to flow up past the motor from below, cooling the motor and allowing air bubbles to rise past the intake rather than into it.
Lower the Pump: If the water table has dropped, you may need to lower the pump deeper into the well to prevent vortexing.
Check the Valves: Inspect the check valve (usually located at the top of the pump). If it is stuck open, water drains back and pulls air in. Replace it if necessary.
Install an Air Relief Valve: These inexpensive valves are installed at the well head. They allow trapped air to escape the line before it travels to your pressure tank or home plumbing.
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Yes. An air lock can cause the pump to run dry. Since the water acts as both a lubricant and a coolant for the motor, running without water can cause the bearings to seize or the motor to overheat and burn out.
Unlike above-ground pumps, you cannot manually "bleed" a submersible pump while it is in the well. To clear an air lock, you typically need to cycle the pump on and off. Turn the power off, wait for the air bubbles to rise out of the impeller stack (about 15 minutes), and try starting it again.
This usually indicates a slow leak in the drop pipe or a faulty check valve. Overnight, the water drains back down into the well, and air fills the pipe. When you turn the water on in the morning, the pump pushes that air out first.
Air in a submersed water pump is more than just a nuisance; it is a symptom of a system that is struggling. Whether caused by dropping water tables, cascading water, or corroded pipes, ignoring the issue can lead to costly repairs.
The best defense against air intrusion is a combination of proper installation depth, regular maintenance, and high-quality equipment. By choosing robust equipment like the stainless steel water pumps from Guangdong Ruirong Pump Industry Co., Ltd., you ensure that your system is built to withstand the harsh underwater environment without corroding or leaking.
If you are unsure whether your current setup is suitable for your well conditions, consult with a professional. Ensuring you have the best water submersible pump for your specific depth and water quality will keep your water flowing smoothly—and air-free—for years to come.