Flow Reduction in Older Water Service Lines
Denver Water Customer Care receives many calls from customers living in older houses with the common complaint of low pressure. After checking our records and asking additional questions about the nature of the problem, it is often identified as low flow rather than low pressure. This document is intended to explain the causes, responsibilities, and solutions for this type of problem.
Q. What Is the Nature of the Problem?
Q. Who Actually Owns the Service Line?
Q. What Is the Solution to the Problem?
Q. What Other Factors Should Be Considered?
Q. What is the nature of the problem?
A. A common problem encountered in older homes in Denver (those built in the 1930s and before) is a reduction of flow rate, often misinterpreted as poor pressure. Many residences built before 1900 have 1/2" taps and 1/2" lead service lines. In later years the common practice switched to 5/8" taps and 5/8" or 3/4" galvanized steel service lines. It was not until the 1950s and 60s that 3/4" taps and 3/4" copper service lines became standard. The expectation of the customer as to what constitutes a reasonable delivery rate has also changed over the past 100 years, accounting for the increase in standard sizing. Those residences with smaller taps and services started out at a disadvantage by today's standards.
Over time, mineral deposits accumulate on the interior surface of the service line pipe. This interior accumulation of minerals and corrosion decreases the interior pipe diameter, and creates a rough inner surface. Both of these contribute to a reduction in flow. The older the pipe, the worse the internal build-up problem and the lower the flow delivery. In many cases, these factors of small initial service diameter and internal deposits combine to reduce flows to as little as 5 gallons per minute (gpm) or even lower. Even in higher pressure areas the increased force created by the pressure in the main might not be enough to overcome the reduction in internal service diameter. Please note that this internal build up of minerals and corrosion does not pose any kind of health threat. In the case of lead pipe, it serves as a protective barrier between the lead and water.
Q. Who actually owns the service line?
A. A typical single family residential service line is 3/4" in diameter, with a 3/4" tap on the water main. Street mains are typically 6", 8", or 12" in diameter. Almost all new service lines are copper. A typical residential service also has a 3/4" meter located in a pit within 5 feet of the property line. In less than 10% of homes, the meter is located inside the house. When a customer wishes to acquire a new service they purchase a tap on the main, which is made by Denver Water personnel. The installation of the service line, stop box (or shut off valve), and meter pit is provided by the purchaser's licensed plumber or contractor. Actual ownership of the service line by the customer starts at the tap on the main. All pipe, valves, and other appurtenances from the tap on into the residence are the property of the homeowner and are their responsibility. Should a break occur on the service line between the main and the stop box, Denver Water will repair the break but will not replace the service line, as it is not our property. Denver Water agrees to deliver water at pressures within the range defined by our Engineering Standards: 40 - 110 psi (actual customer pressure is a function of location and varies from customer to customer). However, no guarantee of rate of flow is provided. Flow rate is typically a function of the size, length, and condition of the service line. Estimated typical flow rate in new service lines is 12 - 16 gpm.
Q. What is the solution to the problem?
A. For most older homes with reduced flow, there are only two solutions: learn to live with the problem, or
replace the service line. The first is not very convenient and the second is very
costly. In cases where the customer does not wish to spend the money to replace the
service line, changing over to some types of water-conserving fixtures (such as low-flow
shower heads and faucet aerators) may help.
Note: Low-flow toilets also can reduce demand on your pipes, but be aware that if the problem is buildup in the incoming pipes, there is a good chance that the outgoing pipes have also been also reduced inside by corrosion buildup, and in such a case, a low-flow toilet may not provide adequate water for flushing.
If outside irrigation is the larger concern, smaller lawn spaces, more efficient sprinker heads, and Xeriscape practices may be effective. If the customer has the money to spend and really wishes to increase the amount of available flow, the best solution is replacement of the service line from the tap on the main all the way into the residence. Keep in mind that water conservation also helps to reduce the water bill.
There are two different practices in service line replacement, one far less expensive than the other. This first type is the replacement of the service line from the residence to the meter. It is much cheaper as it does not require excavation in the street or replacement of the meter pit and stop box. Unfortunately, this replacement rarely solves the whole problem. The old portion of service from the main to the meter remains in bad condition and creates a flow bottleneck. This type of replacement is not recommended and usually leaves the customer with the same problem and a hefty plumbing bill. The best approach is complete replacement of the tap, service, and meter (if necessary) all the way from the main in the street to the residence. A licensed, bonded plumber or contractor should do this type of replacement. In this case, the plumber acquires the necessary permits to excavate the tap connection to the main in the street. After exposing the main, Denver Water personnel can be called to the site to make a new 3/4" tap on the main. All existing Denver Water customers with 1/2" or 5/8" taps are automatically eligible for a 3/4" tap without paying additional System Development Charges (those fees paid by a new customer for a connection). The labor charge varies according to the size of the tap, but it starts at $120 for a 3/4” or 1” tap.
Once Denver Water has replaced the tap on the main, the plumber then connects the new 3/4" copper service to the new tap and extends it on to the residence with a hydraulic pulling machine or in a new trench. With a hydraulic puller, excavations are made at both ends of the pipe and the new 3/4" copper service line is connected to the old service line at one end. The machine then pulls the old service out at the other end, pulling the new service along as it goes. This process requires less excavation than digging an entirely new trench but is not always feasible.
Q. What other factors should be considered?
A. Full replacement of the service line from the main to the residence allows the user to obtain the greatest flow volume possible from the main. It should be stressed that this may not entirely eliminate all problems. A house with an old service typically also has old internal plumbing supplying the various fixtures inside and outside the residence. This internal plumbing is subject to the same build-up and corrosion problems as the service line. This can create an internal bottleneck in delivering the increased water volume, provided by a new service, to those fixtures inside the house and the hose bibs for outside irrigation. This can mean replacement of some or all of the internal plumbing to provide the best possible delivery to each individual point of use.
If you have additional questions regarding the need for service line or internal plumbing replacement, you may wish to contact the Better Business Bureau for a listing of reputable plumbers or contractors. In all cases, it is recommended that the homeowner obtain more than one estimate. Prices may vary dramatically from one contractor to another. It is also recommended that you ask questions and be clear on exactly what work is to be done for what price. Questions regarding the size and date of installation of an existing water tap as well as the actual pressure at a specific location may be directed to Denver Water Customer Care.
Updated: 4/17/2008