Pipes come in many different sizes with differing wall thicknesses from different manufacturers. Uniseals were created for industrial and commercial applications and generally fit what is known as Schedule 40 (a U.S. standard) or pressure pipe which is normally a grey colour and has a thicker wall than let's say normal household waste pipe.

This does not mean that you must use pressure pipe with a Uniseal but rather that you should measure the Outside Diameter (O.D.) of your pipe and match up a suitable Uniseal. There are of course cases where none of the available Uniseals will give a water tight fit with your pipe and you should consider purchasing different pipe.

Matched Uniseal and pipe sizes will provide a seal capable of withstanding around 65 p.s.i., you may not however be using the pipe/Uniseal combination in a pressurised scenario and may find that although your Uniseal is not a really tight fit it is more than adequate to provide a waterproof seal which more than meets your requirements and you do get a feel for what will work and what doesn't. Larger Uniseals have a working tolerance of around 2mm.

The ideal Pipe/Uniseal combination to provide a pressurised waterproof seal are shown in the table below. Simply measure the O.D. of your pipe and match up to the pipe O.D. in the table. Click the Uniseal part number and you will be taken to the correct page to purchase your Uniseals.

Uniseal® Pipe and Holesaw Size Table

 *1 Note 1 - Many websites show the required hole size for the 3/16 inch Uniseal as 10mm - it isn't and this would be realised by anybody who has fitted them. The actual Uniseal hole size for a 3/16" Uniseal required is 8 mm and can be created using a (sharp) drill bit.

*2 Note 2 - Uniseals U025 and U0312, Uniseals U050 and U075, Uniseals U275 and U300, Uniseals U400 and U400-SDR35 require the same sizes of holes. The difference is made up in the thickness of the Alcryn rubber. Uniseals with the same hole size are interchangeable, handy if you have the smaller size and want to increase the flow.

*3 Note 3 - Always measure the Outside Diameter (O.D.) of your pipe. This is the most important size to match into the Pipe O.D. hole size of the Uniseal to create your seal.

Water Flow Per Minute through associated pipework is a rough calculation and assumes gravity feed and low pressure systems.

Pipe I.D. - the Inside Diameter or bore of a pipe and how larger pipe size is denoted e.g. a 3 inch pipe has an inside diameter of 3 inches. Smaller pipes and tubes e.g. 6mm flexible PVC tube are denoted by their outside diameter (just to confuse things a little).

Pipe O.D. - The Outside Diameter of a pipe. This can vary dependant upon pipe type, construction, and manufacturer. An example of this is PVC/ABS pressure pipe which can have a thicker wall construction when the class number (pressure rating) increases. Makes sense when you think about it - higher pressure rating so a thicker wall in the pipe. 

How do you determine what size of pipe you have and if it is suitable - Original Uniseals are ONLY made in Imperial sizes in the U.S.A. to suit their Schedule 40 pipe standards. The simplest thing to do is to measure accurately across the end of the pipe including the pipe wall thickness and match your Pipe O.D. to the table above. Uniseals will work perfectly on any pipe of the right O.D. size. Larger Uniseals have a tolerance of up to 2mm, however if your vessel is not pressurised you will get away with a little more. Some Uniseals fit into the same holesize and so are interchangeable e.g. U275 Uniseals can be directly replaced with U300 Uniseals.

Uniseals for Metric Pipe Sizes - Metric pipe sizes are denoted by the outside diameter (O.D.) of the pipe. An example of this is is a 75mm metric pipe (O.D.) which has an internal diameter (bore) of around 67.8mm. Some metric pipes have a near equivalence in size to the Imperial sized Uniseals so the 75mm metric pipe would fit into a Uniseal U275 for example. To check other metric sized pipes use the Pipe O.D. from the table above.

If you are using standard metric sized household pipes (popular in Hydroponics) the walls are thinner than pressure pipe. The sizes below will fit but check the Outside Diameter of your pipe. Do not assume that the name of the pipe is the O.D. size of the pipe.

The table below indicates which Uniseals work well with metric sized pipe O.D's.

Metric Uniseal® Pipe and Holesaw Size Table

 *1 Note 1 - Many websites show the required hole size for the 3/16 inch Uniseal as 10mm - it isn't and this would be realised by anybody who has fitted them. The actual Uniseal hole size for a 3/16" Uniseal required is 8 mm and can be created using a (sharp) drill bit.

*2 Note 2 - Although our full range is not shown here Uniseals U025 and U0312, Uniseals U050 and U075, Uniseals U275 and U300, Uniseals U400 and U400-SDR35 require the same sizes of holes. The difference is made up in the thickness of the Alcryn rubber. Uniseals with the same hole size are interchangeable, handy if you have the smaller size and want to increase the flow.

Pipe I.D. - the Inside Diameter of a pipe and how larger pipe size is denoted e.g. a 3 inch pipe has an inside diameter of 3 inches. Smaller pipes and tubes e.g. 6mm flexible PVC tube are denoted by their outside diameter (just to confuse things a little).

Pipe O.D. - The Outside Diameter of a pipe. This can vary dependant upon pipe type, construction, and manufacturer. An example of this is PVC/ABS pressure pipe which can have a thicker wall construction when the class number (pressure rating) increases. Makes sense when you think about it - higher pressure rating so a thicker wall in the pipe.

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