A dip tube is a narrow tube that draws liquid from low in a container and routes it to a valve, pump, or inlet for smooth, predictable flow.
Short tube, big job. A dip tube is the skinny straw inside tanks, cans, bottles, and heaters that moves liquid from a low point to a place where it can be used. The idea is simple: place the tube where the liquid sits, seal the top, and the liquid follows the path when pressure or suction is applied. You meet dip tubes in a storage water heater, the sprayer on a cleaner bottle, a CO₂ cylinder made for liquid draw, draft beer kegs, and chemical vessels on plant floors. One part, many tasks.
Because the tube reaches down, the user gets steady delivery without tilting a bottle or tipping a tank. In a water heater, the tube shunts incoming cold water toward the lower region so hot water at the top stays hot. In an aerosol or trigger sprayer, the tube lets the pump sip product from near the base. In a gas cylinder built for liquid service, a metal dip tube reaches the bottom so liquid exits on purpose. In a keg, the liquid tube pulls beer from a precise level inside the shell. Each setting has its own material choices, clearances, and tips, yet the core idea stays the same.
| Where You’ll Find It | What It Does | Notes |
|---|---|---|
| Storage water heater | Sends incoming cold water to the lower zone so heated water stays at the top | Energy Saver: Storage Water Heaters |
| Aerosol can or trigger sprayer | Feeds product from near the bottom to the valve or pump | How Aerosols Work |
| CO₂ or specialty gas cylinder with siphon | Withdraws liquid from the bottom instead of vapor | Airgas: Dip Tube Cylinders |
| Draft beer keg | Routes beer from inside the shell to the faucet line | Liquid tube length sets pickup level |
| Chemical reactor or tank | Introduces or removes fluids below the surface | Often lined PTFE dip pipes or spargers |
What A Dip Tube Is And Why It Matters
Think of a dip tube as the bridge between liquid at rest and the mechanism that moves it. A pump or pressure source applies a push or pull. The tube limits the path, which turns that push or pull into a clean stream. This cuts splashing, air draw, and jumpy delivery. Length and tip shape decide how close the pickup sits to the base, while diameter controls how fast liquid can move at a given pressure.
Because the tube lives inside the container, material choice must match the job. Water heater tubes are usually polypropylene or PEX and run in hot potable water. Aerosol and trigger sprayer tubes are often low-density polyethylene or polypropylene that stand up to common household solvents. Gas cylinders use metal tubes since the service is pressurized and cold in some cases. Keg tubes are stainless steel for sanitation and strength. Process vessels use lined steel or solid fluoropolymer where acids or strong solvents are present. Each case calls for a balance between heat, chemistry, taste, and durability.
Dip Tube Meaning, Parts, And Common Sizes
Core Parts
Across products, a few parts repeat. There is the tube body. At the top, a seal or nipple ties the tube to the inlet or valve. At the bottom, the tip may be straight cut, slotted, or weighted. Some assemblies include a foot filter or check valve to keep debris out or hold a prime. In kegs, a flare sits under the post and an o-ring seals the joint. In process service, a flange or nozzle adapter supports the tube and a liner protects the wetted surface.
Length And Clearance
Most tubes aim to stop just short of the base. That small gap prevents blockage and damage if the container shifts. In a typical residential water heater, the tube runs from the cold inlet at the top down close to the bottom head, which helps maintain a hot layer up top. In a Cornelius-style keg, the liquid tube reaches near the dimple at the center so you can pour the last glass. Some homebrewers switch to a floating pickup that sips from near the surface to dodge sediment.
Materials You’ll See
PEX and polypropylene show up in hot water service. Polyethylene fits many household sprayers. Stainless steel serves food and drink. PTFE linings guard against corrosion in plant duty. Copper and brass appear in older gas cylinders, while modern ones lean to stainless. Each choice weighs heat, chemistry, taste, and cost.
How A Dip Tube Works In Different Products
Storage Water Heaters
Open a hot tap and hot water leaves the top of the tank. The tank stays full because cold water enters through the inlet at the top. The dip tube carries that cold water down into the lower region, where the burner or elements sit. That way, hot water near the top can flow to your tap without instant mixing with new cold water. The U.S. Department of Energy explains this layout on its Energy Saver page, which shows the tank releasing hot water from the top while cold water enters the bottom through the dip tube to be heated again.
Trigger Sprayers And Aerosols
Press the trigger or actuator and a small pump or valve creates low pressure at the top of the tube. Liquid travels up the tube, through the head, and out the nozzle. In an aerosol, a liquefied propellant adds the push from above, while the dip tube acts as the straw. The Aerosol Association describes the path in plain terms. Trigger sprayers follow the same idea with a manual pump in place of the propellant.
Gas Cylinders With Siphon Tubes
Some cylinders ship product as liquid. Those are built with an internal metal dip tube that reaches the bottom. When you open the valve, liquid exits instead of gas. That setup feeds uses that need liquid CO₂, nitrous oxide, or other media. You can see this noted in Airgas literature. Using the right cylinder type matters here, since a non-siphon model delivers vapor only.
Draft Beer Kegs
In a standard ball-lock or commercial keg, the beer line connects to a long stainless tube under the liquid post. Gas enters through a shorter tube under the gas post. The length of the long tube sets the pickup depth. A long tube pours nearly to the last ounce, while a floating pickup draws from the top for clearer beer during service. Brewers pick the style that fits the job, and either choice ties back to the same theme: place the tube where you want the pour to start.
Process Tanks And Reactors
Plant gear uses dip pipes to add, remove, or sparge fluids under the surface. A lined steel pipe can carry acids into the body of a reactor or spread gas through holes along a sparger. The goal is steady placement and controlled contact with the contents. Designers pick wall thickness, liner, and support so the pipe stands up to heat, flow, and movement.
What Is A Dip Tube In Everyday Gear?
People ask the question in many ways because the same part shows up across the house and the shop. In short, it is a tube that reaches down so a device can move liquid up. On a water heater, it shapes stratification so hot water lines see steady temperature. On cleaners and hair sprays, it feeds the pump so you get a full bottle of use. On kegs, it sets where your beer comes from in the shell. On a cylinder, it picks liquid or vapor on purpose. One phrase, many contexts, one job.
Picking Length, Diameter, And Material
Good picks save time and headaches. Length should bring the tip near the base without scraping. A slight chamfer or slot helps prevent a seal at the floor of a vessel. Diameter sets flow: thicker liquids or long runs like a bit more bore; thin liquids need less. The head parts must suit the connection: nipple, flare, or valve body. Material has to match heat and chemistry, keep taste neutral if the liquid is food grade, and last under the forces in play.
When swapping a water heater tube, match the make and length so the tip stays near the lower head. If you work with aerosols or sprayers, trim the tube at a small angle so the tip meets the lowest spot. If you run kegs, choose a standard long tube for full pickup or a floating kit for clear pours after a move. In plant service, follow the vessel drawing and use lined pipe or solid PTFE where called for. Simple rules, steady results.
| Scenario | Pick | Reason |
|---|---|---|
| Residential water heater rebuild | OEM PEX or polypropylene tube, full length | Maintains hot layer at the top for steady taps |
| Household trigger sprayer | LDPE or PP tube cut on a bias | Bias tip reaches the lowest corner of the bottle |
| Liquid CO₂ supply | Siphon cylinder with metal dip tube | Delivers liquid rather than vapor on demand |
| Draft beer keg for clear pours | Floating pickup with silicone hose | Pulls near the surface, away from sediment |
| Chemical reactor charge | PTFE lined steel dip pipe | Resists attack and supports the nozzle |
Care, Cleaning, And Troubleshooting
Water Heaters
Short hot water runs often trace back to a broken or short tube. Plastic flakes at faucet strainers can be a hint. A replacement is a top-side job on most tanks: power or gas off, water off, relieve pressure, remove the cold inlet nipple, swap the tube, and re-seal. The Energy Saver page shows the layout so the steps make sense.
Sprayers And Aerosols
Poor pickup often means the tube is too short or not sitting in the low corner. Cut a new tube to length with a sharp angle at the tip. If the liquid has solids, add a small mesh foot filter. Keep bends gentle so the pump does not draw air.
Gas Cylinders
Know which cylinder you have. A siphon model is built for liquid draw and will spit cold liquid if you expect vapor. A non-siphon model will not feed liquid through a standard valve. Supplier sheets, such as the Airgas document, spell out the hardware and outlet types.
Kegs
Cloudy first pours can be normal if the pickup sits near the base where sediment rests. A short dump clears it. If you moved the keg, a floating pickup helps since it draws from near the top. Keep o-rings clean and posts tight so the tube stays aligned.
Process Gear
Inspect support points and liners on a schedule. Look for wear at the tip and at any holes on a sparger. Verify that the tube clears the vessel floor by the planned gap. Replace seals that sit in hot or aggressive media on time.
Design Notes That Make Life Easier
Avoid Air Pockets
Route the tube with smooth bends and keep joints tight so the pump or pressure source always sees a full column of liquid. A small vent or prime port on process gear can speed startup after service.
Mind The Pickup Gap
A few millimeters of clearance often prevents chatter and blockage. On kegs, the factory tube usually sits in the center dimple. On water heaters, the target is near the lower head without scraping.
Match Tip Style To The Task
Straight cut tips are simple and work in clean liquids. Slots or small cages help in pulpy or foamy products. Weighted ends or floats place the pickup where you want it without rigid support.
Think About Service
Parts that snap in or seal with common fittings reduce downtime. Using common sizes for o-rings and gaskets makes stocking spares easier. Mark the tube length on a tag so the next swap is fast.
Call it a dip tube, a siphon tube, a pickup, or a dip pipe. The shape shifts with the device, yet the idea stays steady: pull liquid from the right place inside a container and hand it to the part that moves it. Pick the right length and material, give it a clear path, and this small part will make the whole system work the way you expect.