Quick verdict
A 1/4 inch NPT thermal relief valve that screws into the pump of many Homelite, Ryobi, DeWalt and Briggs & Stratton gas pressure washers and opens to dump hot water when the pump overheats in bypass, replacing part 678169004 and its Briggs and DeWalt equivalents. A washer left running with the trigger off recirculates water in the pump until it is hot enough to melt seals; the valve vents it before that. A valve that drips constantly or never opens is replaced in five minutes with a wrench.
Strengths
- Protects pump seals from overheating in bypass
- Replaces 678169004 and Briggs 208673GS, 21783GS, 194298GS, B3090GS and DeWalt 17658
- Standard 1/4 inch NPT thread
- Five minute swap with a wrench
- Cheap against a pump rebuild
Weaknesses
- Check the part number on the old valve; pumps vary
- Aftermarket part, not OEM
- A dripping valve may be hot water, not a fault; diagnose first
The overall YardToolLab Score is out of 100. Section scores are out of 10.
What Happens When the Trigger Is Off
A gas pressure washer runs whether or not the trigger is pulled, and with the gun closed the pump recirculates the same cup of water until it is hot enough to cook the seals. The thermal relief valve is the small brass fitting that opens at a set temperature and dumps the hot water on the ground. KBZ’s is a 1/4 inch NPT aftermarket valve that replaces part 678169004 and the equivalent Briggs & Stratton and DeWalt numbers on many Homelite and Ryobi washers.
This review is based on the listing specifications and on how thermal relief valves work on consumer pressure washers generally. We have not fitted this valve ourselves.
Diagnosing the Old Valve
A valve that streams water continuously, even on a cold washer, has failed open and the pump cannot build full pressure. A pump that gets too hot to touch in bypass and never spits water has a valve that is stuck shut, and the seals are next. A squirt of hot water now and then while idling with the gun closed is the valve doing its job.
Fitting
Switch off and let the pump cool. Find the valve on the pump head, usually a small hex fitting with a bleed hole, and unscrew it with a wrench. Wrap the new valve’s thread with two turns of PTFE tape, screw it in snug and no more, and run the washer with the gun closed for a minute to see it behave. Five minutes.
Fit
The listing carries a long list of Homelite and Ryobi models and the Briggs and DeWalt part numbers it replaces. Match the number on the old valve or the washer’s model plate. The thread is standard; the model list is the guide.
Why Bother
A pump rebuild or a new pump costs a large part of a new washer. A valve costs a few dollars and takes a wrench. It is the cheapest maintenance part on the machine and the one most often ignored until the pump is scrap.
Habit That Helps
Do not leave the washer running with the gun closed for more than a minute or two. The valve is the safety net; the habit is what saves the pump.
Who Should Buy It
- Homelite, Ryobi and DeWalt washer owners with a dripping or dead valve.
- Anyone whose washer lost pressure after running in bypass.
- Owners keeping a spare in the washer kit.
Common Owner Complaints
Wrong fit on pumps outside the list. Match the part number.
Alternatives to Consider
The OEM Briggs or Ryobi valve for a guaranteed match. A universal 1/4 inch NPT thermal valve. An unloader valve, which is the other bypass part that fails.
Verdict
For a washer that drips from the pump or loses pressure after idling, the thermal valve is the first and cheapest thing to replace, and this one covers the common Homelite and Ryobi family. Match the number, tape the thread and stop idling with the gun closed.
Full specifications
KBZ 678169004 Thermal Relief Valve 1/4 Inch NPT for Homelite, Ryobi, DeWalt and Briggs & Stratton Pressure Washers FAQs
When the trigger is released the pump keeps running and the water recirculates and heats. At a set temperature the valve opens and dumps the hot water on the ground so cool water enters and the seals survive.
A valve that streams water constantly even when cold has failed open. A pump that gets very hot in bypass and never squirts has a valve stuck shut. Either way, replace it.
With the washer off and cool, unscrew the old valve from the pump with a wrench, wrap the new thread with PTFE tape, screw it in snug and run the washer to check.
Match the part number stamped on the old valve or the model number against the listing. The 1/4 inch NPT thread is common but the model list is the guide.
