Stem
Seat Cylinder
Integral
Stainless Steel
Valve Seat
Disc
Strainer
Screen
Watts Thermal Expansion “Bypass” model water pressure reducing valves
not only control high water service pressure but also contain an “integral
thermal expansion bypass check valve” which reduces the frequency of relief
valve dripping caused by thermal expansion.
The built-in thermal expansion bypass, another Watts first, operates on the
principle of a check valve in reverse. Normally, the check is held closed by
the street main pressure, preventing any flow of water through it into the
system. However, when thermal expansion pressure increases to just 1 lb.
to 2 lbs. higher than the main pressure, the check valve opens passing the
expanding water back into the supply main at the rate it is expanded. Thus,
the expanding water is dissipated (as in an open system) and the relief valve
is not affected.
NOTICE
Effectiveness of the thermal expansion bypass feature is limited to systems
where the street main pressure is less that the allowable setting of the pres-
sure relief valve. Therefore, its use can be broadened by using a relief valve
with higher pressure setting (providing the working pressure of the tank per-
mits). While this feature limits the conditions causing relief valve dripping, it in
no way replaces a pressure relief valve which is necessary to protect against
other causes of excessive pressure.
The use of a water pressure reducing valve nor-
mally creates a closed system. When water is
heated in a closed system, it expands causing an
increase in pressure. This pressure may increase
to the set pressure of the relief valve (on the water
heater) causing it to drip, thus releasing the ex-
panding water and protecting the system against
excessive pressure. This increase in the system
pressure over that regulated by the reducing valve
is call “thermal expansion pressure”.
Watts thermal expansion bypass model water
pressure reducing valve is an economical solution
of this annoyance, since under certain conditions
it allows the expanding water to escape back into
the supply main before it can affect the relief valve.
Complete Replacement Assembly
(Includes Diaphragm)
When Ordering, Specify:
1. Ordering Code Number
2. Size of Valve
3. Type Number
4. Model Shown on Nameplate
ORDERING
CODE NO.
KIT NO. VALVE SERIES SIZE
INCHES
878377 1⁄2" LFN250RK LF23, LF123, LFN250 1⁄2
878339 3⁄4" LFN250RK LF23, LF123, LFN250, LFN256 3⁄4
Diaphragm
Seat and Disc
Assembly
Kit for No. LF23, LF123, LFN250, LFN250B
includes all items shown.
What is - thermal expansion?
Series LF23, LF123 and LFN250
For additional detailed information on thermal expansion
send for folder F-RV.
IS-2323A 1315 EDP# 1910259 © 2013 Watts
USA: Tel: (978) 688-1811 • Fax: (978) 794-1848 • www.watts.com
Canada: Tel: (905) 332-4090 • Fax: (905) 332-7068 • www.watts.ca
Limited Warranty: Watts Regulator Co. (the “Company”) warrants each product to be free from defects in material and workmanship under normal usage for a period of one year from the date of
original shipment. In the event of such defects within the warranty period, the Company will, at its option, replace or recondition the product without charge.
THE WARRANTY SET FORTH HEREIN IS GIVEN EXPRESSLY AND IS THE ONLY WARRANTY GIVEN BY THE COMPANY WITH RESPECT TO THE PRODUCT. THE COMPANY MAKES NO OTHER
WARRANTIES, EXPRESS OR IMPLIED. THE COMPANY HEREBY SPECIFICALLY DISCLAIMS ALL OTHER WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
The remedy described in the first paragraph of this warranty shall constitute the sole and exclusive remedy for breach of warranty, and the Company shall not be responsible for any incidental, special
or consequential damages, including without limitation, lost profits or the cost of repairing or replacing other property which is damaged if this product does not work properly, other costs resulting
from labor charges, delays, vandalism, negligence, fouling caused by foreign material, damage from adverse water conditions, chemical, or any other circumstances over which the Company has no
control. This warranty shall be invalidated by any abuse, misuse, misapplication, improper installation or improper maintenance or alteration of the product.
Some States do not allow limitations on how long an implied warranty lasts, and some States do not allow the exclusion or limitation of incidental or consequential damages. Therefore the above
limitations may not apply to you. This Limited Warranty gives you specific legal rights, and you may have other rights that vary from State to State. You should consult applicable state laws to
determine your rights. SO FAR AS IS CONSISTENT WITH APPLICABLE STATE LAW, ANY IMPLIED WARRANTIES THAT MAY NOT BE DISCLAIMED, INCLUDING THE IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ARE LIMITED IN DURATION TO ONE YEAR FROM THE DATE OF ORIGINAL SHIPMENT.
A Watts Water Technologies Company
WARNING: This product contains chemicals known to
the State of California to cause cancer and birth defects
or other reproductive harm.
For more information: www.watts.com/prop65
