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Re-piping a Domestic Water System

By Stephen Varone, AIA and Peter Varsalona, PE

Our 15-story, 60-unit pre-war cooperative in Manhattan has been hampered by an aging plumbing system that has slowly grown worse over the years. Our problems include low water pressure, brownish water, scalding showers, and leaky overhead pipes in the basement, which have damaged a storage area. All of these items obviously need to be addressed, but because of the extent of work required, we’re not sure how best to proceed. Are piecemeal repairs feasible to ease the budgetary demands and the inconvenience to residents, or is it best to bite the bullet and tackle the full-scale upgrade all at once?

The plumbing problems you cite in an older building like yours are very likely caused by galvanized steel piping that has slowly corroded over the years. Unfortunately, the conditions cannot be fixed easily one by one—i.e., first the water discoloration, then the low pressure, then the leaks, etc. The most common way to correct the deficiencies is to replace the old piping in your building with new copper tubing.

A complete re-piping of a building’s domestic water system is an expensive and disruptive undertaking. It involves demolition of walls and floors, water shutoffs, possible asbestos removal, and plenty of patience on residents’ part. While the piping replacement program can be performed in phases over several years to stretch out the costs of the repairs, this approach will end up costing more in the long run than replacing it all together, which in itself could still take a year or more. In addition, performing the piping replacement as a whole will enable the building to correct any system-wide defects rather than just replacing in kind one section at a time. So if your board has the funds in place, it’s recommended that your cooperative face the full-scale upgrade head on.

Particular attention should be paid to problem areas and known deficiencies. The engineer or consultant will want to distribute a questionnaire to residents asking them to report conditions in their apartments, as this is a particularly effective diagnostic tool. Some top-floor residents, for example, may complain of low water pressure, while someone on a lower floor might have suffered water damage from a burst pipe resulting from high pressure. Discolored water, on the other hand, is likely to affect all residents. Superintendents and maintenance staff are also a valuable source of information regarding the history of plumbing problems and repairs and everyday conditions in the building.

Based on the results of the questionnaire, the engineer/plumbing consultant will visit selected apartments, as well as the common areas within the building, to evaluate the system components in more detail. They will try to locate low-pressure zones in the system, and may perform pressure tests on identified sections. Occasionally, investigative probes and removing sections of wall are required to check the condition of leaking or broken pipes.

Culprit: Corrosion
One of the first components of the plumbing system to examine is the piping. In old buildings, domestic water piping is most likely made of galvanized steel. As galvanized steel ages, it starts to corrode on the inside, forming a buildup of rust and scale over time. As these particles flake off, they give the water a brownish discoloration.
A buildup of rust and scale may also be contributing to the low water pressure or flow in your system. The mineral deposits that form on the inside of galvanized steel pipes reduce the available diameter for water to flow through. In very old, corroded pipes, the buildup can be so severe that a large percentage of the interior is blocked, sometimes reducing water flow to a mere trickle.

In addition, corroded pipes will eventually lead to leaks in the system, as in your building’s mains and risers. Mains are the overhead pipes usually found in the basement; risers carry water vertically to the different floors. While localized sections can be replaced at the leaking points for a short-term fix, they are often a precursor to major bursts down the line. Once a pipe bursts, that line or section of the building’s system must be shut off until the damaged piping is replaced.

A break in branch line piping, which carries water from the risers to the individual apartment fixtures, will necessitate a shutdown of water to that particular unit. Many older buildings, however, do not have operable shut-off valves for branch lines, which means a riser or even the building’s entire water supply would have to be turned off if a branch line bursts.

Replacing galvanized steel pipes with copper tubing constitutes the major element of most major domestic plumbing upgrades. Copper is much more resistant to corrosion and scale buildup than galvanized steel is, and it can last as long as 80 years. Installing new copper tubing will go a long way toward alleviating the problems your building has been having with the low pressure and discolored water.

In a typical domestic water system upgrade, a parallel system of copper tubes is installed alongside the existing mains and risers. Rather than “replacing” the old mains and risers, per se, they are often left abandoned in place. Working on badly corroded large mains and risers can loosen rust and scale within, creating clogs and perhaps bursting branch lines. The parallel configuration prevents damage to the old pipes, which would require their immediate replacement in kind before the new tubing is up and running. In addition, removing old risers requires further demolition of walls and floors as well as a possible disturbance of asbestos-containing material covering the old piping. (Keep in mind that asbestos-containing material should be removed only by a licensed asbestos abatement firm.)

The re-piping sequence usually proceeds from the largest pipes to the smallest. First are the building mains or overheads, which connect the city’s main to the building’s domestic water supply. Risers are installed next, starting from the top floor down, usually one apartment line at a time.

Risers often pose the most difficult part of the re-piping because in some areas of the building, there may not be much room left in a chase (the space behind or along a wall in which the risers run) to install new piping. Finding a new chase nearby can be challenging because structural or mechanical elements, such as beams or vents, may be in the way, or because apartments may have been combined or reconfigured, using up a previously available empty space. In such cases, the engineer will have to redesign a new plumbing line that reroutes around building elements, is mostly hidden from view, and does not take up too much useable space. Closets, stairwells, and abandoned shafts and fireplaces are common places to locate a new chase. On rare occasions, new piping lines are run outside of buildings, but that configuration is often more expensive and visually unpleasing.

Last installed are the branch lines, the small (½- to ¾-inch diameter) pipes that run from the risers to individual apartments, where they connect to toilets, sinks, faucets, and other plumbing fixtures. Branch lines commonly run two or three feet above the baseboard, and installing them requires removing portions of the wall and shutting off water for a few hours during the day. (The contractor tries to work within the schedule of those residents who are home during the day. Residents should not have to go without water overnight.) A typical branch line installation takes approximately three days per apartment.

In some very old systems, a portion of the galvanized steel branch line piping may still be in fair condition, even though the risers and mains are badly corroded and must be replaced. Connecting new and old piping of different metals (copper and steel), however, can cause the metals to react to each other, resulting in corrosion and dislodging existing buildup. Therefore, it is usually recommended that galvanized steel branch line piping be replaced wherever it joins with a newly installed copper riser. (A special dielectric material can be installed between the two dissimilar metals to negate the reaction if they must be connected.) Typically, residents pay for new branch line piping to their apartments, and the cooperative or condominium pays for the rest of the upgrade.

All cold water piping should be wrapped with fiberglass insulation and a vapor-retardant paint at the joints to prevent condensation from forming, which can lead to moisture and mold behind walls. Additionally, the inside of the new copper tubing must be cleaned and sterilized with a solution after installation.

New Fixtures
Some boards and residents use the opportunity during a re-piping to upgrade plumbing fixtures as well. For example, buildings with old-style flushometer toilets, which use up to nine gallons per flush, may want to consider switching to tank toilets, which typically use only 1.6 gallons per flush. For those residents who’ve been jumping out of the way of scalding showers, a pressure-balancing mixing valve, which combines hot and cold water into a single temperate stream, will bring relief.

Boards may also want to consider installing a cushion stop tank, a pressurized tank that delivers water for small requests during off-peak usage time, such as late at night. A cushion stop tank reduces wear and tear on the building’s booster pumps because they don’t have to kick in for every small request for water.

As part of the upgrade, the engineer should make sure the building has the proper backflow preventer in place and working properly. Backflow preventers, which are mandated by New York City’s Department of Environment Protection, are valves that prevent the building’s water supply from reversing course and returning to the city’s main (caused by back pressure or back siphonage, for example, by an open fire hydrant), potentially contaminating the city’s water supply to other buildings. Older plumbing systems often have a simple check valve in place, but depending on your building’s DEP status, it may require a double-check valve or a more specialized reduced pressure zone (RPZ) valve if your building has medical or dental offices or commercial tenants.

To minimize the inevitable disruption to residents, it is recommended that the board keep them up to date on the scheduling of the re-piping program and let them know what to expect. The contractor is responsible for sealing doorways so dust and debris from cutting through walls and floors doesn’t enter other rooms of the apartment. Residents, however, should be reminded to remove furniture, rugs, clothes, art work, and any other items that could be damaged. In older buildings, lead paint may also pose a risk during demolition, so the board may want to consider hiring an environmental consultant as a precaution.

A full-scale domestic piping upgrade is no doubt a financial burden for a cooperative to bear, and a major inconvenience for residents. But properly planned and performed, you and your fellow shareholders will eventually be enjoying clean, clear water and strong, hot—but not scalding—showers.

Stephen Varone, AIA is president and Peter Varsalona, P.E. principal of RAND Engineering & Architecture, PC. This column was originally published in the November 2005 issue of Habitat Magazine.

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