How to Make Good Plumbing Pipework Connections
‘Making the right connections’ is vital where plumbing is concerned. There is a wide range of fittings to meet every situation likely to be encountered in fitting domestic pipework – though there are cases where it may be advisable to bend the pipe mechanically. Modern fittings are simple to use.
There are five situations where you may need to use a plumbing fitting. These are where it is necessary to join two lengths of pipe in a straight line; to allow the introduction of a branch connection; to facilitate a change of direction; to control the flow of water, either mechanically or automatically; and to release air or drain-off water.
Because of the high cost of fittings, and since these are a possible source of flow resistance and turbulence, use of fittings should be avoided if a mechanical bend-either using a spring or pipe-bending machine-can produce the same result.
A change of direction may also influence the water-flow characteristics. A tight bend may disrupt the smooth, forward impetus of water. For this reason, sharp changes of direction should be avoided.
In some cases a bent coupling or elbow may have to be used in tight spaces. It is always advisable to use, where possible, the slow-bend type of fitting. This fitting, with its larger radius, reduces the breaking force which is exerted in changes of flow.
Other larger-radius fittings which help to maintain this uninterrupted flow pattern are the sweep tee and the curved tee.
Flow resistance can be created by the careless use of jointing materials, such as non-toxic plumbing compound, used to consolidate joints, hemp and PTFE tape. The latter has tended to supersede hemp and jointing compound as a means of sealing threaded joints against leaks.
Such materials can easily creep past the pipe ends and form an obstruction and cause turbulence. The removal of burrs from pipe ends is equally important.
Choice of connectors
There are two types of pipe connectors: the compression fitting and the capillary fitting. These break down into two further types, the manipulative and non-manipulative compression fitting. Solder fittings are either pre-soldered or of the unsoldered, end-feed type.
The choice is governed by various factors. In some cases, access may not allow the use of a spanner to tighten compression fittings, and a soldered one may have to be used. Aesthetically, a solder fitting is neater than a compression one and is also cheaper.
For the inexperienced person, the compression fitting is more reliable, for a leaking soldered joint is more difficult to correct, and some skill is needed to make these joints.
A leaking compression joint can usually be corrected by slightly tightening the locking unit on the fitting; however, overtightening can distort the tube and cause leaking which may be difficult to cure.
The manipulative fitting is seldom used in domestic plumbing or heating. Using this entails ‘belling’ out the mouth of the tube with a special tool, the mouth of which is then compressed about the body of the fitting. The union is completed by tightening locking nuts.
Compression fittings rely on the compression of a metal cone or ferrule, usually made of anealed brass or copper and commonly called an olive, against the external wall of the pipe. When the nuts of the fittings are tightened, the olive effects a watertight seal.
If the tube is not pushed fully home to an internal stop or shoulder and held in position when the lock nuts at each end are tightened, a poor joint may result. A machine-moulded ridge within the fitting prevents the tube from travelling further than the correct depth.
Equally, the pipe should be cut squarely; if it is not, it may be a potential source of leaking. Check finally that there are no flow-inhibiting burrs before connecting the lube.
Although compression fittings are made to a general pattern, it is important to use the type of olive made for the fitting. Some olives have a longer chamfer on one side than the other, and this long chamfer should be inserted to enter the body of the fitting.
It is a wise provision to apply a little jointing compound over the olive. This is not specified by manufacturers but helps to ensure a watertight joint.
Modern thin-wall copper tube is easily distorted out of shape. Some three-quarters of a turn, after tightening the fitting by hand, is usually adequate for joints on fittings of up to 28mm. Use the second spanner to hold the body of the fitting while you tighten each nut.
If you are making a number of connections, either complete each before proceeding to the next, or mark each after connecting so that none is overlooked for subsequent tightening. It is surprisingly easy to forget to tighten a fitting.
10. November 2011 by admin
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