roduced, photocopied, transmitted, or
stored in any retrieval system of any nature, without the written permission of the copyright owner. www.apc.com Rev 2006-0

2





Executive Summary
Chilled water remains a popular cooling medium; however leaks in the piping systems are a
threat to system availability. High density computing creates the need to bring chilled water
closer than ever before to the IT equipment, prompting the need for new high reliability
piping methods. This paper discusses new piping approaches which can dramatically
reduce the risk of leakage and facilitate high density deployment. Alternative piping
approaches and the advantages over traditional piping systems are described. 2006 American Power Conversion. All rights reserved. No part of this publication may be used, reproduced, photocopied, transmitted, or
stored in any retrieval system of any nature, without the written permission of the copyright owner. www.apc.com Rev 2006-0

3
Introduction
In data centers, the traditional approach to piping distribution has been to use hard copper or carbon steel
piping with welded, brazed or threaded fittings for routing and branching of the piping to the air conditioners.
Since every fitting used in the piping line increases the leak failure potential in the data center, piping
distribution is generally located under the raised floor where channels or trenches are sometimes built under
the pipe to capture water in case of any leaks or rupture. This approach worked in static data centers, where
there was no need to relocate or add air conditioners.

With the current trend of increased densities in IT equipment and more frequent moves, additions, and
changes, air conditioners must occasionally be added to the traditional lay-out where the use of hard piping
becomes problematic. These additions require new piping to be installed, increasing deployment time of the
equipment and increasing the risk of down time associated with the installation. The result is that there is a
need in the industry for a more flexible modular system of piping that can better accommodate changing
requirements.

A new trend is data centers that do not use a raised floor. These hard-floor installations are enabled by
newer cooling technologies and architectures that do not require a raised floor for air distribution. For many
users this allows additional flexibility of placement of data centers and computer rooms. One result of this
trend is that overhead piping has become more common. Leaks in overhead piping can be even a greater
risk to system downtime and damage than underfloor piping. There is a need in the industry for a more leak-
resistant piping system.

A further trend in data center design is the deployment of cooling at the IT equipment row locations (In-row),
or even to individual racks, rather than at the room level. This is done to allow higher density and greater
electrical efficiency, and is discusses more completely in APC White Paper #130, The Advantages of Row
and Rack-Oriented Cooling Architectures for Data Center. This type of deployment forces the air
conditioning units and the associated piping closer to the IT equipment. Again this situation requires a more
reliable, modular, and scalable piping system.

The use of seamless flexible piping eliminates the use of intermediate fittings, mitigating the risk of water
leaks, reducing deployment time, and increasing the agility of the system. This paper explains this new
piping technology and its application to next-generation data centers.

Characteristics of traditional hard piping methods
The use of hard copper or carbon steel piping is the traditional approach in data centers. Carbon steel pipe
schedule 40 and hard copper pipe type L or M are most commonly used. Hard piping requires the use of
threaded, grooved, welded or brazed fittings at every turn, at every valve, at every branch to multiple air 2006 American Power Conversion. All rights reserved. No part of this publication may be used, reproduced, photocopied, transmitted, or
stored in any retrieval system of any nature, without the written permission of the copyright owner. www.apc.com Rev 2006-0

4
conditioners and at every 1.8 or 6 meters (6 or 20 feet), depending on the available length of the pipe run. It
is common to have multiple fittings in one pipe run from the chilled water source to the air conditioner.

Failure modes of hard piping
Each threaded or welded fitting presents a leak potential for the chilled water system. One common reason
for leakage is the threading process which removes 50% or more of the pipe wall beginning on day one and
weakens that joint.

Another reason for pipe failure and water leakage is galvanic corrosion, where the carbon steel pipe directly
meets a brass valve, or is transitioned to copper pipe. "Galvanic" corrosion occurs between any two
dissimilar metals in contact with each other and water, and typically attacks the steel pipe to a degree
somewhat dependent upon existing corrosion conditions. It is visually recognizable in its latter stages by
some degree of deposit buildup where the dissimilar metals meet at the threads, creating a micro-fine leak.
At that point, however, most of the damage has already occurred and replacement of that pipe is required,
otherwise the leak size would increase as corrosion advances.

Electrically isolating fittings, called dielectrics, are used for connections between dissimilar metals in most
piping systems. Dialectric fittings are specified by most consulting and design engineers, but it is not
uncommon to find installations where they were not installed or they are installed incorrectly.

In a traditional chilled water installation, it is not uncommon to see a main carbon steel supply or return pipe
that branches to the air conditioners with copper piping, so multiple dielectric fittings might be used if several
computer room air conditioners (CRAC) are in the data center.

Other less common reasons include the failure of the thread sealant over time, poor machining of the
threads, gasket deterioration in grooved connections and poor quality of the pipe or fittings, vibration, stress,
improper assembly, or excessive operating pressures beyond design.

In hard piping systems, minerals tend to build up on the interior wall causing scaling and oxidation of the
copper and eventually creating pinholes and leakage in the piping. Mineral build-up overtime also increases
the pressure drop in the water line, especially when it is deposited in elbows or fittings. To avoid this
problem, water has to be treated and maintained periodically to ensure proper PH levels. The water is
usually treated at the time of start-up and during regular services. Even though it is rare to see pinholes in a
closed loop chilled water installation, it has been found in installations were poor maintenance was
performed.

Condensation also presents a problem in a chilled water system. Chilled water piping is usually insulated to
prevent condensation in the piping exterior. However, it is not uncommon to find moisture on the piping
fittings where multiple elbows, connections, and fixtures such as valves, strainers, and gauges make an
effective insulation job difficult. Any crack or sealing failure in the insulation presents water potential in the 2006 American Power Conversion. All rights reserved. No part of this publication may be used, reproduced, photocopied, transmitted, or
stored in any retrieval system of any nature, without the written permission of the copyright owner. www.apc.com Rev 2006-0

5
data center and it also becomes an entry point for moisture to permeate under the insulation and travel
along the pipe surface for a significant distance.

The presence of condensation at the outer pipe wall in non-conditioned environments also produces
corrosive effects. Exterior corrosion is promoted much more when high humidity exists in the environment
surrounding the pipe. In extreme cases, condensation will build up to the point where the insulation becomes
completely saturated with water. In data centers, exterior corrosion of the pipe does not usually occur due to
the humidity controlled environment.

To contain any condensation or water in the event of a leak in a data center, some IT managers and
facilities engineers demand additional protection for the IT and electrical equipment. However, this practice
is generally not implemented until water becomes a problem in the data center.

In some instances, the concern about the possible loss of cooling that a single leak would cause is so great
that IT managers opt to install a completely redundant hard piping system which doubles the total piping
installation cost. Alternatively, they opt to install CRACs with a refrigerant based system as a back-up that
also requires additional refrigeration piping.

Underfloor hard piping installation
The method for routing chilled water piping depends on the size of the room and the number of air
conditioners. For small rooms, the chilled water piping is usually routed through one large main supply and
return pipe made of carbon steel or copper. For larger rooms, several large manifolds of carbon steel pipe
are used. Each main header or manifold is then branched with copper piping to each air conditioner. Figure
1 illustrates underfloor hard piping where multiple fittings are used in the installation.

For this methodology, when the owner is concerned about water under the floor, a trench with drains is
specifically built for the containment of the chilled water piping to separate it from the electrical wiring.
Alternatively, a drain pan can b