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Frequently Asked Questions About
CPVC |
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1- Where should I use CPVC ?
CPVC is designed for use in hot and cold Water distribution systems. CPVC
systems are ideal for all portable Water piping requirements in a typical
single family home, apartment, motel, codominium, mobile home, manufactured
housing, light commercial and institutional strurer. Other hot water piping
applications such as central heating, radiant floor heat and solar may be
suitable for CPVC. However, we urge you to check with the heating unit
manufacturer prior to using CPVC in these applications.
2- What is the expected life of a CPVC water
distribution system ?
CPVC piping systems have been installed and operating since 1960, and these
early installations are still performing faultlessly - over 40 years of
trouble- free use. CPVC system design and standards incorporate significant
engineering safety factors which should translate to a long service life. CPVC
plumbing systems have a design service life of 50 years. CPVC piping is not
susceptible to corrosion. Electroly size or scale build-up in areas where
water, soil and / or atmospheric conditions are aggressive. We firmly believe
that CPVC plumbing systems will provide a service life as long or longer than
alternative materials on market.
3- will a CPVC systems offer a financial advantage to
owners in terms of utilities expense ?
Yes. the thermal conductivity of a metal system is 2500 times than of a CPVC
system. the improved insulating characteristics associated with CPVC can
generate long-term savings for an energy conscious home-owner or tenant. CPVC
will keep water hot for a much longer period of time than metal tubing.
4- How do I use CPVC if I run under a concrete slab
?
When using CPVC under a slab, you must pressure test the system before pouring
the slab. Also, it is wise to use 1" foam insulation pipe sleeve at
changes in direction, where the pipe comes out of the slab, and at construction
joints. the pipe should be evenly supported in comes out of the slab, and at
construction joints. the pipe should be evenly supported in smooths bottom
trenches the backfill should be free of rock and debris which could damage the
pipe.
5- Should specific types of primers and solvent
cements be used on CPVC system ? are specific colors required ?
Solvent cement used should always be for CPVC use specifically, and
manufactured to meet the requirements of DIN 8080 - 8079 & AStmF493 or
equivalent. All-purpose cements should be utilized. Purple primer manufactured
for PVC pipe is acceptable . Orange CPVC solvent cements facilitate
identification. Unpigmented CPVC solvent cement and primers are available and
are acceptable in various jurisdictions. Clear cement / primer provides neater
finished appearance.
6- I have been told that CPVC tubing ends may split
during installation. Why should this occur ? How can these cracks be prevented
?
Most crack are initiated by rough handling. This handling can occur during
shipment, while being inventoried at the wholesaler, or while on the job sight.
Also, fine cracks an be caused by cutting the pipe with dull or damaged ratchet
cutters when temperatures are below 10?C. the vast majority of crack occur
during colder weather months. When ambient temperatures are below 10?C, CPVC,
like most other plastics such as PP, PEX, PVC-U, may become somewhat brittle
and should be handled more carefully. To reduce problems resulting from cracked
product, several measures can initiated:
- Educate your installers. Make them aware of the potential problem and
instruct them to handle CPVC in appropriate way.
- Use a saw or a circular tubing cutter with a plastic cutting blade (ridged
# 151P or similar) to cut your pipe to length.
- Inspect pipe ends thoroughly prior to making a joint . Should a crack be
evident, cut off any split portion before proceeding.
- During cold weather, gripping the tubing tightly around the area to be cut
about 10 seconds prior to making the cut will warm the tubing and reduce
possible problems
7- What about CPVC piping in walls ?
CPVC may be embedded within walls, prvided the following points are respected:
- Embed firmly firmly in the wall, with the piping contained continuously by
concrete. (The other alternative is to allow the pipe to move freely under
thermal expansion. Problems will occur if the pipe is neither completely
embedded nor able to expand freely) concrete should be homogeneous, without
gravel or stones which risk damaging the pipe. Ensure that the is at least 2.5
cm. from outside surface.
- Do not embed demountable fittings.
- At exist and entry points, protect piping with a sleeve.
- Pressure testing should be done before concrete is poured.
As the pipe thermally expands, tensile stresses will be developed. Concrete
will contain the CPVC. Other materials may not, e.g. plaserboard. the developed
tensile stress, s, is given by the equation: s=C.T.E C=Coefficient of thermal
expansion
 T=Temperature change
E=Youngs modulus
This calculated developed tensile stress may be compared to the surrounding
material ( plastboard, concrete, etc.) to give an indication whether the
material will contain the pipe, or whether the pipe will crack the wall.
For CPVC:
C=6.3 × 10-5 cm/cm°C
E=2650MPa
8- Is CPVC resistant to U.V. exposure ?
If we compare CPVC to some other commonly used piping materials.
Polyethylene and polypropylene:
U.V. acts as a strong catalyst for the oxidation process which breaks down the
polymer chains, leading to weakness in the pipe and loss of hydrostatic
strength.
CPVC:
The main degradation process is dehydrochlorination, Whilst sightly accelerated
by UV, dose not break down the polymer chains to any significant extent after
outdoor exposure, being mainly limited to a surface discoloration effect. There
is a loss of impact resistance due to the impact modifies losing efficiency.
This may even result in increased modulus.
- There is no significant loss in stress bearing capability
- 30 years of outside service in southern California.
- Impact resistance mainly an installation issue (before any UV exposure).
If a portion of the piping system will be lift exposed to U.V. light, a
standard grade of exterior, latex paint will protect the pipe adequately.
9- Is CPVC quieter than metallic system?
Yes, we can compare the velocity of sound in CPVC to that in copper and water.
The velocity of sound in :
CPVC=1350 m / s
COPPER=3600 m / s
WATER=1473 m / s
The sound will travel in the material with the fastet possible velocity. This
means that in a copper system, the sound travels in the copper, whilst in a
CPVC system, sound travels in the water and the system is as quite as
physically possible.
10- What about scale build up ?
Scale build up is a function of the roughness of the pipe, as measured by the
Hazen-Williams "C" factor used in Hazen-Williams formula for
calculating friction head losses in piping systems.
| Higher value for C |
Less friction |
| |
Less head loss |
| material |
C Factor |
| |
New |
After 4-40 years |
| CPVC |
150 |
150 |
| copper / steel |
130-140 |
60-120 |
With metal systems, once corrosion attack starts, (e.g. the green color when
copper reacts with chlorides in water to form copper chloride) this starts a
vicious circle leading to scale build up. With CPVC, there is no corrosion and
hence scale build up is inhibited.
11- Is condensation reduced with CPVC ?
Yes, for a given ambient air temperature and water temperature in the pipe, the
relative humidity must be 10-15 % higher with CPVC to get the same degree of
condensation. For the same humidity level and water temperature can be ±
10°C higher than for copper to get the same degree of condensation. |
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