Install Instructions
IS-ETX/ETSX
Installation Instructions
•  Inlet Connection: 
1
/2" (15mm) MNPT-ETX-15, 
1
/2" (15mm) MNPT-ETX-30,  
1
/2" (15mm) MNPT-ETX-60, 
3
/4" (20mm) MNPT-ETX-90,  
1" (25mm) FNPT-ETSX-30, 1" (25mm) FNPT-ETSX-40, 
1" (25mm) FNPT-ETSX-40, 1" (25mm) FNPT-ETSX-60, 
1
1
/4" (32mm) FNPT-ETSX-90, 1
1
/4" (32mm) FNPT-ETSX-110, 
1
1
/4" (32mm) FNPT-ETSX-160
“Attention Installer: After installation, please leave this 
instruction sheet for occupant’s information.”
Series ETX may be installed in a tee or any other suitable tap-
ping in the heating system and can be installed in a vertical or 
horizontal position. Series ETSX are floor models.
Caution: Tank must be supported in horizontal 
position to prevent damage to the tank.
Maximum temperature: 220ºF (104ºC) 
Maximum working pressure: 
75psi (517 kPa) (ETX-15, ETX-30, ETX-60). 
100psi (6.9 bar) (ETX-90, ETSX-30, ETSX-40, 
ETSX-60, ETSX-90, ETSX-110, ETSX-160).
Installing the Expansion Tank
•  Follow all instructions and local codes during the installing 
of this product.
•  Tanks are precharged to 12psi (83 kPa) and should be 
charged to the system pressure prior to installation in the 
system.
Caution: Do not exceed the maximum pressure rating of the tank.
After installing the ETX/ETSX Expansion Tank
•  Fill system. Vent air from system.
•  Fire the burner to bring system to design temperature.
•  After initial venting of air, additional air will vent as water 
is heated. Installation of the Watts AS Air scoop and 
FV4 Automatic Vent Valve will provide automatic air venting.*
*Refer to Air Scoop and Automatic Vent Valve instruction 
sheets for proper installation.
•  Check system pressure after water is heated. If pressure 
is too high, drain water from boiler and adjust feed water 
pressure regulator (typically 12psi) (83 kPa).
Service Hints
1.  If the system pressure is too high: 
a. Check gauge calibration. 
b. Check to see if the ETX/ETSX tank has lost it’s air charge.
Note: To get an accurate reading when checking ETX/ETSX 
tank air pressure with any tire gauge, disconnect the tank 
from the system.
c.  Check for faulty fill valve operation. First close manual 
shutoff located before the fill-valve, then draw system pres-
sure down to 12psi (83 kPa) (or other preset pressure) and 
observe system for pressure buildup several hours later.
d.  Check for service water entering system from any other 
source such as a defective tankless heater. Use same pro-
cedure as above after shutting off possible water source.
2.  If pressure relief valve drips water: 
a.  First, check system pressure. If too high, follow steps 
1.a, b, c, and d above.
b.  If pressure relief valve continues to drip water, even at 
reduced pressure, flush relief valve by quickly raising lever 
several times. If drip continues, replace relief valve. (see 
caution below)
c.  If multiple ETX/ETSX tanks are installed in the system, 
check pressure of each for possible air leaks. Be sure air 
valve caps are on tight.
Caution: Relief valve will discharge hot water, therefore precautions must 
be taken to avoid scalding injury or water damage. A proper drain line 
connected to the valve outlet and run to a safe place of disposal must  
be installed.
Watts Series ETX, ETSX 
Hot Water Heating System Expansion Tanks
For Closed Hot Water Heating Systems
IS-ETX/ETSX  0845  EDP#1915894  © Watts, 2008
USA: 815 Chestnut St., No. Andover, MA 01845-6098; www.watts.com
Canada: 5435 North Service Rd., Burlington, ONT. L7L 5H7; www.wattscanada.ca
Water Safety & Flow Control Products
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.

