Laboratory Rubber and PVC Tubing

Rubber tubing is the standard choice for connecting Bunsen burners to gas taps and for general bench connections where flexibility and a tight grip on barbed fittings matter most. It resists kinking under bending and forms a secure seal over standard laboratory barb sizes. Inspect rubber gas tubing periodically for cracking, perishing, or hardening, and replace it as part of routine laboratory safety maintenance.

Clear PVC hose is the right choice whenever you need to see the contents flowing through the tube — siphoning, gravity liquid transfer, or monitoring flow rate by eye. PVC is more rigid than rubber, which helps it hold its shape over longer runs, but it is less flexible around tight bends. Check the chemical compatibility of PVC with the specific liquid being transferred, as it is not suitable for all organic solvents.

Silicone vacuum hose has a thicker wall designed to resist collapsing under negative pressure, making it the correct choice for vacuum filtration, vacuum desiccation, and aeration setups. Silicone also tolerates a wider temperature range and resists ozone degradation better than standard rubber, giving it a longer service life in continuous-use applications such as aquarium or fermentation aeration.

Tubing must be sized to fit snugly over the barb or nozzle it connects to — too loose and it will leak or blow off under pressure, too tight and it will be difficult to fit and may split. Measure the outside diameter of the barb fitting and choose tubing with a bore diameter slightly smaller than this measurement, since rubber and silicone stretch slightly to grip. For condenser and vacuum connections, a snug fit secured with a hose clip gives the most reliable seal.

Carrying gas, vacuum or liquid between pieces of apparatus. The commonest job is running gas from the tap to a Bunsen burner. Beyond that it connects a filtration flask to a pump, feeds cooling water through a condenser, and links apparatus during distillation.

Silicone. It stays flexible across a much wider temperature range than rubber or PVC, and it does not go brittle or sticky with age the way natural rubber eventually does. PVC is the least heat tolerant of the three and should stay well away from a flame.

Most school laboratory gas taps and Bunsen burner inlets use a barb sized for tubing with an internal bore of around 8 to 10 mm. Check both the gas tap nozzle and the burner inlet, as some equipment uses slightly different bore sizes. A snug push-fit over both ends without forcing is the goal — if the tubing slides on too easily it may not seal properly under gas pressure.

Standard clear PVC tubing handles water and most dilute aqueous solutions well but is not resistant to many organic solvents, which can cause it to soften, swell, or degrade. For applications involving solvents, oils, or aggressive chemicals, use silicone or a chemically resistant tubing material instead, and always check a chemical compatibility chart before exposing PVC tubing to an unfamiliar reagent.

There is no fixed universal interval, but rubber gas tubing should be inspected regularly for cracking, hardening, or perishing and replaced as soon as any of these signs appear, since a damaged gas line is a safety hazard. Many school laboratories replace gas tubing annually as part of routine safety maintenance regardless of visible condition, particularly where tubing is exposed to sunlight or heat, both of which accelerate rubber degradation.

Thin-walled tubing is not designed to withstand the negative pressure created during vacuum filtration and will collapse inward, restricting or stopping flow. Use tubing specifically rated for vacuum use, which has a thicker wall and often a reinforced or braided construction to resist collapsing. If collapsing continues with vacuum-rated tubing, check that the bore size is not undersized for the vacuum pump's flow rate.