Water-supply systems lead pipes

What about artificial water supply systems Maybe just enclosing the flow from reservoir to final user in watertight pipes is sufficient to ensure that the laws of supply and demand will apply. We can imagine a pipe leading from a reservoir situated in the hills 1000 m above the user, open at the level of the reservoir but terminated by a tap at the level of the user. Opening the tap will make the water flow closing it will make it stop. Not only that, but we can obtain a less-than-maximal flow by opening the tap only partially. 

Rome in the first century of the Christian era had a remarkable water supply system administered by a body of officials comparable to the modern Water Board. The chief officer was the Curator Aquarum the supply of water was taken from nine different sources, including springs and lakes from io to 60 miles from the city supplies suitable for potable purposes were kept apart from less pure waters which were used for public fountains, baths and sanitation. Each length of pipe bore raised inscriptions formed by impressions in the sand bed in which the lead sheet was cast. The inscriptions indicated the person authorised to receive the water. 

There are two different types of water sprinkler systems, wet-pipe and dry-pipe. The lines leading to the sprinkler heads are full of water in a wet-pipe system so that water will be discharged immediately from an open sprinkler head, while in a dry-pipe system, the lines are full of air under pressure instead of water. This latter type of unit should be used where the temperature is not maintained above freezing at aU times. Both types of systems include a main control valve which is designed not only to supply water to the sprinkler heads but also to provide a mechanism to cause an alarm to sound. The valves also usually provide a visual indication of whether they are open or closed. Except during maintenance, they should be in the open position. There are a number of design features for these valves which are beyond the scope of this document, except to note that some are intended to avoid false alarms due to surges or variations in the water supply pressure to the system. 

Use of lead materials—The use of solder or flux containing more than 0.2% lead or pipes and pipe fittings containing more than 8% lead is prohibited in public water supply systems. Public notification is required where lead is used in construction materials of the public water supply system, or where water is sufficiently corrosive to cause leaching of lead from the distribution system or lines. 

The extent of occurrence of lead pipes in the water supply system. 

Lead several approaches can be used in combination to demonstrate the success (or otherwise) or corrective actions (i) benchmark monitoring at selected houses which have lead pipe-work (see Section 3.4), (ii) lead pipe test rigs at strategic locations (see Section 10.2), and (iii) zonal surveys - random daytime samphng from consumers taps wiU provide the most representative check of variation across the water supply system. 

This simple approach was used in the plumbosolvency control programme in Wales (Hayes et al., 2008) and enabled a zonal emission model to be calibrated that good validation of predicted RDT sample results was obtained from actual RDT sample results indicated that this simple methodology was adequate for estimating the percentage of houses with a lead pipe. However, to put this into perspective, over 11,000 results were available across 29 water supply systems, with an average of 383 RDT sample results per scheme. 

There are three basic issues in lead pipe rehabilitation (i) lead pipe lateral rehabilitation on the public portion of the water supply system that runs from the water main to the water meter or stop-cock (curb-stop) (ii) lead pipes on the private portion of the water supply line from the meter or stop-cock to the house and (iii) lead pipe-work within the house. Whilst the only 100% control method will be the removal or all lead pipes, there are substantially less expensive alternatives available consisting of chemical treatment and internal cathodic protection. Total lead pipe removal also has the problem of split ownership and responsibility, disturbance, and destruction of land-scaping (external) and decoration (internal). 

Every drinking water supply system has its own individual characteristics (most importantly, the corrosivity of the water supply and the extent of occurrence of lead pipes), albeit generic groupings do help to develop corrective strategies and set priorities. 

As described in Section 10.2, lead pipe test rigs can be installed at strategic locations within a water supply system. A typical deployment would be (i) treated water at the treatment works, before orthophosphate dosing, (ii) treated water at the treatment works, after ortho-phosphate dosing, (iii) within the near distribution system, close to the treatment works, and (iv) within the far distribution system, distant from the treatment works. 

In practice, the ortho-phosphate dose required is also a function of the percentage reduction in plumbosolvency needed to achieve the optimisation criterion, which is strongly influenced by the extent of occurrence of lead pipes within the water supply system. In the Wales (UK) case smdy (Hayes et al., 2008), the required percentage reduction in plumbosolvency and the required average ortho-phosphate dose was established for a total of 29 dosing schemes that were subject to regulatory control, plus 9 others not subject to regulatory control. 

For a population of 100,000 and an average residency of 2.5 people per dwelling, the water supply system will serve 40,000 dwellings. If 50% of these dwellings (i.e., 20,000) have a lead service pipe, the replacement cost will be between 10 M and 40 M. If 25% of these dwellings (i.e., 10,000) have a domestic lead pipe, the replacement cost will be between 5 M and 20 M. 

The concentration of orthophosphate used in the UK varies from 0.5 to 2.0 mg/1 (P), most typically between 1.0 and 1.5 mg/1 (P), and is generally two or even three times higher than that dosed in the US (IWA, 2010). Doses are water supply system specific, and are determined by both water quality and the extent of occurrence of houses with lead pipes. Higher doses have been used in supplies that have an elevated organic contenfi particularly where humic substances are involved (Cardew, 2009). No problems have been reported in relation to bacterial growths within distribution networks and the impact on sewage effluent is considered slight (IWA, 2010). 

This project commenced on a firm basis due to the model s extensive and successful track record from the optimisation of numerous water supply systems in the UK. The calibration data on non-lead pipe-work is not a major influence on the... 

Rabin (2008) relates how old municipal water systems used lead pipes to dehver water to homes. This was recognized as a public health threat in the 1800s, and in the early part of the twentieth century municipalities began to prohibit lead service lines. This movement was countered by the Lead Industry Association (LIA), which began a public campaign to commend the benefits of using lead pipes. Problems remain to this day, as the federal Lead and Copper Rule (LCR) requires water companies to initiate lead water pipe replacement when lead levels in water exceed 15 parts per billion (ppb). But the LCR allows water utilities to replace only the public portion of lead pipes. The private portion of these pipes, from the main service line to a house, can be left in place. Renner (2007) describes that when partial replacement is undertaken, that disturbance results in a rise in lead levels in water. Millions of homes in the U.S. have lead service lines as part of their water supply systems (McCartney 2010). 

ISO 2898-1 1996 Plastics - Plasticized poly(vinyl chloride) (PVC-P) moulding and extrusion materials - Part 1 Designation system and basis for specifications ISO 2898-2 1997 Plastics - Plasticized poly(vinyl chloride) (PVC-P) moulding and extrusion materials - Part 2 Preparation of test specimens and determination of properties ISO 3114 1977 Unplasticized polyvinyl chloride (PVC) pipes for potable water supply -Extractability of lead and tin - Test method... 

An important source of lead leading to human exposure is that contained in drinking water. Treatment processes for public water supplies are unlikely to reduce the concentration of filterable lead in the raw water, except where processes such as precipitation water softening are used [25]. Fortunately, however, the concentrations of lead in the raw water are generally fairly low, <0.01 mg dm". Many tap water samples, nevertheless, reveal significantly elevated lead levels, which may occasionally rise to over 1 mg dm . These elevated concentrations are found in areas where the plumbing system is based on lead pipes. 

The tap water Pb problem was especially acute for certain communities in Scotland with lead plumbing components in their residential units and soft, corrosive water in highlands impoundments. Of particular note was the finding that parts of Scotland and Wales with particularly corrosive water supplies also had housing stock with old, lead plumbing-based water systems. This included lead pipe for street connections and lead-lined storage tanks in the cities of Glasgow and Ayr (Richards and Moore, 1984 Sherlock et al., 1982). 

If a water supply area fails to comply with the AL for lead then optimal corrosion control treatment must be determined and then implemented, and a programme of lead service line replacement for pipe segments owned by the public water system must be subsequently initiated at a minimum rate of 7% per annum. 

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