Plastic v Copper Domestic Plumbing systems

[webmaster]

Copper has been used in the building industry for a considerable period, replacing lead. Copper is tried and tested; it works, although it is not without its disadvantages (see later). For some years now plastic pipe has been used by the water companies for providing supplies from the mains. These systems are very easy to install and are very reliable, today plastic systems are available for use in homes for both DWH (domestic hot water) and CH (central heating). This section of the FAQ is intended to explain the differences in the use of copper and plastic to allow balanced decision to be made about its use.

The author's experience of plastic systems is limited to Hep20 supplied by Hepworth, although there are other suppliers and there details are listed at the end of this section.

Lets first look at copper systems; they broadly fit into two camps compression and solder fittings.

Solder fittings come in two types end feed which has no solder ring and Yorkshire which has a quantity of solder already inside the fitting. It is largely a matter of personal choice which system is used, end feed is cheaper but requires more skill to fit. The quality of joint formed depends on the cleanliness of the fittings and pipe before applying the heat, the correct amount of flux and the correct application of heat.

Compression fittings for copper fit into two types, those with a brass olive that are tightened with a spanner and push fit. The old style compression fitting (with the brass olive) is made by placing a length of pipe into a fitting the outer nut compress the olive to both hold the pipe and form a water seal. The push fit fittings have two devices that perform the action of the olive, a grab ring and an o ring. Most of the plastic fittings will also work with copper.

Plastic systems consist of lengths or coils plastic pipe and compression fittings; these compression fittings are of the push fit type with a grab ring and an O ring. Assembly of the joint is simple, the pipe must be cut cleanly at 90 degrees and a stainless steel support tube inserted into the pipe, the pipe is then pushed home into the fitting. If the pipe is pushed home it cannot be removed without taking the fitting apart (some fittings cannot be disassembled)

Now we understand the basic systems lets look at how the installation procedure differs between copper and plastic, for the purposes of this we assume that copper is done in solder fittings.

Because plastic can be cabled it is very easy to drill joists and just thread it though, of course this is not possible with copper (there is some soft copper pipe which can be cabled), in practice the 15mm pipe is very easy but the 22mm is more difficult because the pipe is much more rigid.

Cabling the pipe has other advantages: -

Lower noise, every fitting that you add to a copper system will generate some noise
High flow rates, because of fewer fittings and many bends can be gentle
Speed of installation, read cost less risk of nail damage, if you notch out a joist for a copper pipe you run the risk of nail damage later.

An advertised benefit is fewer fittings, but remember that copper fittings are a fraction of the cost of plastic, so this one does not hold water (pun intended).

The materials used in the Hep2o system are: - Pipe polybutylene, Grab Ring stainless steel (new versions have a grab ring encased in plastic), O Ring propylene diene monomer, spacer mineral filled polyamide.

The operating pressure of the Hep2o is dependent on the temperature. see below
20oC 12 Bar (174 psi)
60oC 9 Bar (131 psi)
80oC 7 Bar (102 psi)
90oC 6 Bar (87psi)

These are operational pressures not test pressures. Assuming normal cycling these will give a minimum life of over 50 years, however these pressures are above those normally encountered in a domestic situation. The pipe will also stand limited operation at 100oC however it is not recommended to use the system when using solid fuel as temperatures of 100oC could last for a considerable time.


Regards, Webmaster
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Regards, Webmaster