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.

*3 Note 3 - Always measure accurately the Outside Diameter (O.D.) of your pipe.

Pipe sizes are often printed somewhere along the length of the pipe. To give you an example standard 40mm household pipe which is usually solvent welded (glued) is normally 43mm O.D. (and is a tough fit into a Uniseal U125) A better fit can be achieved in a U125 however with standard 40mm push fit pipe which actually has a smaller O.D.

Uniseal Vs rigid bulkhead - measuring the O.D. is also important if you want to use a rigid bulkhead to fit your pipe but even more so. There is no flexibility in the size of the bulkhead hole into which you can insert your pipe, any excess space would need to be taken up with an extra thick coating of solvent on both parts and will lead to ultimate failure. Distributors of pipes and bulkheads will always recommend using "matching sets" from the same manufacturer. Or tried and tested sets from different manufacturers. Measure your rigid bulkhead and your pipe O.D. before you start! This can be an expensive learning process if you are not careful.

Buying your pipe - I buy my pipe from here - www.pipestock.com in the UK. Not sure that it is the least expensive but they have all of the sizes I need and they seem inexpensive, a 3 metre length of ABS 1" pressure pipe costs around 8.00 UKPounds for a 3 metre length, and they deliver reasonably quickly. Using pressure pipe ensures that my pipework stands up to the rigours of the weather outside, not something that household piping is designed for.

Creating your hole - The Uniseal Shop exclusively sells suitable inexpensive quality drill bits, holesaws and arbors as Uniseal Holesaw Kits to achieve a good hole into which you can fit your Uniseal. You will find these on the same pages as the Uniseals themselves. Be careful using an old/worn holesaw. The quality of your seal is directly dependant on the quality of the hole you create. Even the best quality brand new commercially available holesaws have a tolerance of 0.2mm. If you want to use your own existing holesaw or a really cheap set you can buy on eBay then that may be good enough.

The Uniseal Shop only sells Uniseal Holesaw Kits complete as sets with Uniseals, holesaw and arbor. This helps to keep the postage and packaging costs down per installation since the holesaws and arbors can be weighty items and greatly increase the postal costs. 

Downloadable Image

Downloadable Imperial Uniseal Hole Size Chart Image

Downloadable Metric Uniseal Hole Size Chart Image