Although the use of lead for new plumbing purposes has long been prohibited, it is not uncommon to find it still installed in older properties. Most homes built before the 1950’s depended on either iron or lead pipe-work for their water supply.
As new plumbing materials were developed for transporting water and gas supplies, most accessible lead plumbing was removed from buildings as part of a normal upgrading of supply networks. In domestic properties, the need to facilitate water supplies to new appliances took advantage of the versatility of copper. Copper pipes were easy to work with and could be cut and joined to accommodate any requirement.
Lately, plastics have started to replace copper as a lightweight and durable alternative. Water supply companies have utilised plastic pipes on a grand scale to upgrade their deteriorating and previously poorly maintained supply networks.
However, it is not uncommon to still find some older domestic properties still supplied with potable water from a lead rising main. Lead pipes are usually conspicuous by their dull, grey colour. When the soft, grey surface is scraped away, the shining, silvery material that is exposed will provide confirmation.
Wherever possible, these old lead rising mains should be removed and replaced with a suitable alternative material. A lead rising main may still be present in an older building for a variety of reasons. It might simply have been overlooked.
Not surprisingly, the most common reason for leaving a lead rising main, and the rest of the lead pipework supplying it, in place is the cost of replacing it. The cost of removing and replacing old lead pipes back to the boundary of the property must be met by the property owner. In many cases, this considerable cost provides a disincentive.
How much of a health risk is perpetuated by leaving a lead main in place is a matter of conjecture. Undisturbed lead pipes can develop an interior coating of mineral deposits that inhibit the transfer of lead into the potable water supply.
Where a homeowner has concerns about a possible health hazard from existing lead pipework, water testing will indicate whether lead is a problem.
Perhaps one of the most common problems to occur with an existing lead rising main is leakage around an old copper to lead union. In the past, internal lead pipe-work was removed and copper was joined to the remaining lead main using a soldering technique called ‘wiping’.
A wiped joint was created by stretching the cut end of the remaining lead mains and inserting a length of clean and fluxed copper pipe into the widened and cleaned neck. Widening the neck also produced a cupped shape, which had a practical purpose. Firstly, a suitable length of metal rod was inserted into the top of the copper pipe and extending into the lead pipe to prevent movement between the two pipes. Then, bar solder was melted with a blowtorch and allowed to fill the cup on the lead pipe neck. This formed a union between the two pipes. The solder was gradually built up by periodically wiping the molten material with moleskin, or other suitable cloth to form something resembling a thick bandage. Part of the skill was to complete this task without melting the lead.
Although this procedure was prohibited by the Water Regulations some years ago, it is still regarded as a true plumber’s skill and is sometimes used as a temporary measure to repair leaking unions.
Over time, these previously wiped joints are susceptible to corrosion. This is often caused by the electro-potentially dissimilar properties of copper and lead. The corrosion eventually causes leaks in the wiped union that need to be repaired.
To repair on old copper to lead union, or to install a copper ‘T’ component into a lead pipe, a brass coupling called a lead-lock or other similar brass or plastic compression fittings are now the only couplings permitted for joining onto lead.
With the mains water turned off, the old wiped joint can be removed with a hacksaw, or the lead pipe cut at a suitable position to accommodate the lead- locks.
A lead-lock compression fitting works by creating a tight seal onto the lead pipe by utilising an internal gripper and friction ring to compress a large rubber ‘O’ ring against the surface of the lead pipe. This forms a watertight seal. The lead-lock fitting is made of brass, and so eliminates the problems associated with connecting dissimilar metals. The opposite end of the lead-lock has normal compression fittings to accommodate conventional copper or plastic pipework. Other permitted joining components use a similar technique.
Where possible, a small cut-off section of the lead pipe should be taken to the plumber’s merchants to ensure that the correctly sized lead-lock is obtained. Old lead pipes were manufactured in different gauges and were usually categorised by weight. Each different weight corresponded with a particular diameter.
Where it is not possible to remove a section of lead pipe for comparison, possibly because the remaining lead pipe is too small, a length of cotton can be wrapped around the lead pipe, and where one end joins another, the cotton can be cut. This piece of cotton, when measured, will provide the circumference, which when divided by 3.142 will establish the lead pipe diameter.
Nevertheless, when trying to fit a suitable lead-lock, it may be necessary to file away any external grooves or raised surfaces on the lead pipe to ensure a snug-fitting ‘O’ ring and water-tight connection.
It is also very important to prevent the soft lead pipe from kinking, bending twisting or deforming when applying tension to lead-lock couplings during tightening. A suitable set of grips applying an opposite force will prevent this problem occurring.
When completing the join, the mains water should be turned on gradually and the new connection closely monitored for signs of leakage. Where a leak is detected, the lead pipe can be filed to modify it and the fitting replaced or sometimes adjusted and re-fitted.
Unfortunately, a lead rising main is often located in the most inaccessible of places and working on it requires considerable patience and manual dexterity. If this is the case, it is often more appropriate to employ the services of a qualified plumber to undertake any connections to a lead main. Where a subsequent joint failure occurs due to an incompetently installed fitting, insurance cover for water damage may be affected.
After disturbing any existing lead plumbing, it is a wise precaution to run the cold-water tap for ten minutes or so to flush through any minute lead fragments that may have become dislodged. It is also good practice to run cold water through a lead supplied drinking water outlet for a few minutes prior to using, particularly if the water tap has not been operated for a day or more.
Although no longer used for installations, old lead pipe-work can continue to provide safe water for domestic consumption. However, where possible, old lead pipes should be removed.