VIP-Polymers are recognised as the leading global manufacturers of Tyton-SIT self restrained gaskets for ductile iron pipe and as a result, our Tyton-SIT gaskets are selected as original equipment by many of the leading global producers. Each design has been thoroughly tested in accordance with EN545:2010/ EN598:2007 and our Tyton-SIT fully comply with the requirements of BS6920 as well as holding WRAS material approval at temperature of up to 60º.

What is Tyton-SIT?

  • Designed to suit Tyton® socket (DIN28603)
  • Self-restrained gasket used to joint ductile iron pipes to EN545/ EN598
  • Used by all major pipe manufacturers globally since 1970’s
  • Around 45% of pipe joints in Europe are self-restrained

 VIP-Polymers have been manufacturing Tyton SIT since the 1970’s and to date, have supplied over five million units worldwide.

These are self-anchored joints which eliminate the need for thrust blocks at changes in direction, making them particularly suitable for difficult or unsuitable ground conditions such as soft ground or subsidence-prone areas; where space is limited; steep inclines or under rivers.


Benefits of Tyton SIT Vs Concrete Thrust Blocks:

  • Concrete thrust blocks are often impractical due to unstable ground (i.e. groundwater)
  • Contractors/ Engineers use far more concrete than the design stipulates “just in case”
  • Difficulty pouring in freezing conditions
  • Environmentally unfriendly; the cement industry is responsible for 5% of worldwide man made carbon dioxide (CO2)
  • Expensive to dispose of soil matter removed from trench
  • Impractical and can cause disruption in city centre excavations
  • In congested trenches, not always possible to pour thrust blocks without interfering with other utilities


thrust-block   restraint-joint
Traditional concrete thrust block   External Mechanical Restraint Joint

Benefits of Tyton SIT Vs External Mechanical Restraint System

  • External mechanical restraint systems cost considerably more
  • More difficult to install as access needed to reach bolts beneath the joint
  • Entire assembly needs to be protected from corrosion
  • Larger trench needed compared with Tyton SIT EXTRA
  • Installation time of Tyton SIT typically 35% of the time taken to install External Mechanical Restraint
  • Quicker installation
  • Better for the environment
  • Less disruption
  • Lower installation costs
  • No large excavation required


Table of Tyton SIT Maximum Working Pressures:

Nominal Diameter (mm) Operating Pressure Maximum Working Pressure Maximum Test Pressure Maximum Deflection Degree
DN100 30 bar 35 bar
DN150 22 bar 27 bar
DN200 22 bar 27 bar
DN250 22 bar 27 bar
DN300 20 bar 25 bar
DN350 20 bar 25 bar
DN400 16 bar 21 bar 



VIP-Polymers have further developed the thrust resisting properties of the proven TytonSIT® sealing system. Currently available in sizes DN450, DN500 & DN600, these gaskets are available for Ductile Iron Pipe manufactured in accordance with EN545 and EN598.

Tyton SITextraTytonSIT EXTRA®

The additional thrust resisting properties of the Tyton SIT EXTRA® has been achieved through revising the geometry of the locking “teeth” on the chromium retaining segments contained within the gasket. These segments lock themselves into the surface of the pipe and convert the thrust forces into the socket and spigot assembly. Full testing in accordance with EN545 has been carried out and further information is available upon request.

Table of Tyton SIT EXTRA® Maximum Working Pressures:

Nomimal Diameter (mm) Operating Pressure Maximum Working Pressure Maximum Test Pressure Maximum Deflection Degree
DN450 16 bar 21 bar
DN500 16 bar 21 bar
DN600 16 bar 21 bar


As an alternative to Tyton®, VIP-Polymers has also developed and patented Viptyte™. This is a seal for push-fit flexible joints in iron pipes. It:

  • Is specially profiled
  • Is made of single hardness rubber
  • Can be used for the same socket design as for the Tyton® gaskets.




BS6920. Suitability of non-metallic products for use in contact with water intended for human consumption with regard to their effect on the quality of the water.

ISO 3302-1:2014. Specifies classes of dimensional tolerances and their values for moulded, extruded, and calendared solid rubber products.

BS EN 681-1. Elastomeric seals. Material requirements for pipe joint seals in water and drainage applications.

ISO 2230:2002. Rubber products. Guidelines for storage.

BS EN 598:2007+A1:2009. Ductile iron pipes, fittings, accessories and their joints for sewerage applications. Requirements and test methods.

BS EN 545:2010. Ductile iron pipes, fittings, accessories and their joints for water pipelines. Requirements and test methods.

Benefits of products:

  • Moulded Seals available for pipes up to 2200mm Diameter
  • Designed to fit DIN28603 sockets and suitable for pipe manufactured in accordance with DN545 & EN598
  • Material fully WRAS approved and BS6920 compliant – up to 60º
  • Approved for use in Germany, France, Middle East, as well as a number of other countries globally.