You may also like
Manufacturer Resources
Product Specs
- Application:
- Boiler
- Body Material:
- Iron
- Gpm When Relieved:
- Does Not Apply to Product
- Inlet Connection Size:
- 3/4 IN
- Inlet Connection Type:
- Female Threaded
- Inlet Thread Type:
- NPT
- Maximum Temperature:
- 250°F
- Maximum Temperature Fahrenheit:
- 250
- Maximum Working Pressure:
- 10
- Outlet Connection Size:
- 3/4 IN
- Outlet Connection Type:
- Female Threaded
- Outlet Thread Type:
- NPT
- Pressure Range:
- Does Not Apply to Product
- Pressure Relief Setting:
- 30 PSI
- Pressure Relief Setting Psi:
- 30
- Pressure Steam Discharge Capacity:
- 550,000 BTU per hour
- Protection Type:
- Pressure
- Series:
- 374A
- Shank Length:
- Does Not Apply To Product
- Temperature Relief:
- 9999°F
- Temperature Relief Fahrenheit:
- 9999
- Temperature Steam Discharge Capacity:
- Does Not Apply to Product
- Test Lever:
- Yes
- Thermostat Material:
- Does Not Apply To Product
- Thermostat Probe Length:
- Does Not Apply To Product
- Department:
- Plumbing
- Product Group:
- Plumbing
- Product Subgroup:
- Valves
- Product Type:
- Relief Valve
- UL Listing (Specs):
- N-No UL Code Rating
Watts 358553 – Frequently Asked Questions
1) Will the Watts 374A 0358553 relief valve thread into a 3/4 inch NPT boiler tapping?
Yes. The Watts 374A, model 358553, has a 3/4 inch female NPT inlet and a 3/4 inch female NPT outlet, so it threads onto a 3/4 inch male nipple off the boiler and takes a 3/4 inch male-threaded discharge pipe. Both ends are female, so you will need nipples on each side, not a straight slip fit.
2) Is a 30 psi relief valve correct for a residential hot water boiler?
The 374A model 358553 is set to relieve at 30 psi, which is the common setting for a closed-loop hydronic heating boiler. The rule is that the valve setting must not exceed the boiler's maximum allowable working pressure stamped on the boiler nameplate. If your boiler is rated above 30 psi you can use this valve, but if it is rated below 30 psi you need a lower-set valve instead.
3) Is this a pressure-only relief valve or a combination temperature and pressure valve?
Pressure only. The 374A 358553 protects against overpressure and has no thermostat probe, so it is not a T and P valve. For a water heater, where code calls for combined temperature and pressure protection, you need a T and P valve with a probe, not this one. On a hydronic heating boiler the pressure relief valve is the standard fitting.
4) What boiler size will a 550,000 BTU relief valve cover?
The 374A 358553 has a steam discharge capacity of 550,000 BTU per hour, so it suits boilers with a gross output at or below that figure. Sizing rule for relief valves: the valve's relieving capacity must equal or exceed the boiler's rated input or output as marked. A boiler putting out more than 550,000 BTU/hr needs a larger valve or a second one.
5) What is the maximum temperature the Watts 374A relief valve can handle?
250 degrees F is the top operating temperature for the 374A 358553. That covers normal hydronic supply temperatures with margin. It is not a temperature-actuated valve, so it will not open on heat alone; it opens on pressure at 30 psi.
6) Does this Watts boiler relief valve have a test lever?
Yes, the 374A 358553 comes with a manual test lever, so maintenance staff can lift and flush the seat during routine service without pulling the valve. That matters on facility service schedules where the relief valve gets exercised annually.
7) What is the body made of on the Watts 0358553 relief valve?
Iron body with a forged brass inlet. The iron body suits standard hydronic boiler service; the brass inlet is the threaded connection going into the boiler tapping.
How fast can I get the Watts 358553 delivered?
Most orders ship the same day from our distribution partners, with quick delivery throughout the
continental
U.S.
Need it urgently? Contact Us for expedited shipping options.
Can I return it if it doesn’t work for me?
Yes—ZenSupply offers a hassle-free return policy. If the product isn’t the right fit,
reach out to our support team for a return authorization or setup a return by following our return instructions.
Does the Watts 358553 come with a warranty?
Absolutely. The Watts 358553 is backed by a manufacturer’s warranty.
For full warranty terms, check the product documentation or Contact Us.
How do I get technical support or installation help for the Watts 358553?
You can call, text, or email our expert support team for fast answers. We’re here to help with
product
selection,
installation tips, and troubleshooting. Contact Us
Why buy the Watts 358553 from ZenSupply?
ZenSupply makes it easy to get the commercial door hardware you need—fast shipping, expert support,
and
rewards on
every order.
Our team is always ready to help you choose the right product for your project.