These products, when intended for HDPE pipe systems and installed according to the manufacturer's instructions, provide sealed, axially restrained joints. Unless otherwise specified, it is generally recommended that all couplings used with HDPE should have a stiffener installed to increase the sealing capability of the coupling by minimizing the effects of creep and dimensional changes due to temperature variations.
The above list, which is not necessarily in order of priority, is not intended to suggest that other mechanical solutions or products are not acceptable, including new products that continually evolve or are being introduced, but primarily to provide a starting point for those utilities that have not yet determined their own acceptable repair solution.