PVC Pipe Jointing
During manufacture PVC pipes are cut to standard length by cut-off saws. These saws have carbide-tipped circular blades which produce a neat cut without burrs.
However, pipes may be cut on site with a variety of cutting tools. These are:
- Proprietary cutting tools – These tools can cut, deburr and chamfer the pipe in one operation. They are the best tools for cutting pipe.
- A portable petrol-driven ‘quick cut saw – This is quick and easy to use. However, care must be taken and some deburring will be required
- Air-driven tools – This produces a neat, clean cut. It does, however require a compressor.
- A hand saw and mitre box – This saw produces a square cut but requires more deburring. It takes comparatively more time and effort and requires a stand.
The use of roller cutters is not recommended.
Solvent Cement Joints
Vinidex recommends Vinidex solvent cements and priming fluid for use with Vinidex PVC pipes and fittings, thus ensuring a complete quality system. Vinidex premium solvent cements and priming fluid are specially formulated for PVC pipes and fittings and should not be used with other thermoplastic materials.
The following procedure should be strictly observed for best results. The steps and precautions will allow easy and efficient assembly of joints. Users may refer to AS/NZS 2032 – Installation of PVC pipe systems, for further guidance.
Incorrect procedure and short cuts will lead to poor quality joints and possible system failure.
Solvent cement joint principles
Vinidex offers three types of solvent cements formulated specifically for pressure and non-pressure applications. They are colour coded, along with the primer, in accordance with AS/NZS 3879:
- Type ‘P’ for pressure, including potable water installations, designed to develop high shear strengths with an interference fit (green solvent, green print & lid)
- Type ‘N’ for non-pressure applications, designed for the higher gap filling properties needed for clearance fits (blue solvent, blue label & lid)
- Type ‘G’” gap filling for parallel or low interference pressure and non-pressure joints (clear)
- Priming fluid for use with all solvent cements (red priming fluid, red label & lid)
Always use the correct solvent cement for the application.
Solvent cement jointing is a ‘chemical welding’, not a gluing process. The priming fluid cleans, degreases and removes the glazed surface thus preparing and softening the surface of the pipe so that the solvent cement bonds the PVC. The solvent cement softens, swells and dissolves the spigot and socket surfaces. These surfaces form a bond into one solid material as they cure.
Note: PVC-O pipes are not suitable for solvent cement jointing.
Rubber Ring Joints
Jointing rings are supplied with the pipe, together with a lubricant suitable for the purpose. Other lubricants may not be suitable for potable water contact and may affect the ring. They should not be substituted without specific knowledge of these effects.
The ring provides a fluid seal in the socket of a pipe or fitting and is compressed when the spigot is passed into the socket. Check the label on the pipe socket. Series 1, Series 2, sewer rings or rings from other manufacturers cannot be interchanged.
Some Vinidex pipes incorporate a captive Rieber ring that is pre-installed in the factory and must not be removed in the field. This will be identified on the socket label.
Vinidex Superlink ductile iron fittings have been designed with deep sockets to be suitable for PVC pressure pipes in all situations.
The depth of sockets on pipes and fittings must be sufficient to accommodate the axial movements due to the combined effect of a number of factors, such as thermal contraction and Poisson contraction which occurs when a pipe is pressurised. The Poisson effect is more significant for PVC-M and PVC-O pipes because of their higher operating stress. Vinidex Superlink ductile iron fittings have socket lengths adequate for all situations and are recommended for use with PVC pipe.
Use of Other Brand Fittings
A variety of other cast/ductile iron, bronze, aluminium, steel, ABS and PVC fittings may be used with Vinidex PVC pipes. In most cases the fittings have sockets that are shorter than pipe sockets. When the socket is too short for the spigot to be inserted to the witness mark, the pipe should be fully homed and special precautions should be taken during construction to ensure that no contraction of the pipe will be taken up at these joints, i.e. it should be taken up at other joints.
The main functions of a flanged joint is to create a demountable joint, to connect valves and vessels where strength in tension is required, or to joint to other materials.
The three types of flanges available are:
- Full-faced PVC socketed flanges.
- PVC socketed stub flanges with loose PVC or metal backing rings.
- Tapered cores with either metal or PVC flanges.
Flange joints require gaskets to seal them. In high stress situations, metal backing plates or flat washers are also required to spread the force and prevent damage to the flange. Bolts should not be over tightened. Epoxy-coated aluminium or ductile iron flange adaptors are also available.
For normal water supply purposes, the cutting of threads on PVC pipes is not an acceptable practice. A moulded threaded adaptor should be used.
When making threaded joints the following points should be observed:
- A thread sealant is recommended, and the only acceptable material is PTFE (TEFLON) tape. Hemp, grease or solvent cement should never be used. Test the ‘fit’ of the joint, particularly when connecting to other materials or to other manufacturers’ fittings. Judge the amount of tape accordingly. Under no circumstances should the thread bottom against a stop on either the male or female fitting.
- Hand tighten initially. Usually a further two more turns are sufficient to effect a seal. Tighten only just enough to seal, plus half a turn more.
Over tightening will over stress the fitting. Avoid using serrated grip tools particularly on the plain barrel of fittings or pipes.
- If a threaded connection is made to a metal fitting, it is preferable that the male thread be PVC. For female PVC fittings special care should be taken to avoid overstressing.
GOLDEN RULE: Do not overtighten!
There are various types of compression joints available for use with PVC pipes. In principle, all of these affect a seal by mechanical compression of a rubber ring by means of threaded caps or bolted end plates. Because immediate pressurisation is possible such joints are generally preferred for repair work.
They are also used frequently for final connections in difficult situations where slight misalignment cannot be avoided.
When making compression joints the manufacturers’ recommendations should be followed. Over-tightening should be avoided. It may be found advantageous to use a lubricant on the rubber ring.
Connection to Other Materials
A wide range of adaptors to joint PVC pipes and fittings to pipes and fittings of other materials is available.