General Pump 36311770 3/8" BSPP Bypass Nipple Orifice - 3266

Designed to Restore Proper Bypass Flow and Ensure Safe Pressure Control

The General Pump 36311770 is a precision-machined 3/8" BSPP bypass nipple orifice engineered to restore correct bypass flow and safe pressure control on compatible General Pump unloader valves - ensuring stable system pressure, reliable unloader cycling, and reduced downtime for your pressure washer.

Why You'll Love the General Pump 36311770

This small but critical OEM component is the reason a high-pressure washing system transitions smoothly between trigger-on and trigger-off states. When the existing nipple is worn or damaged, replacing it with the 36311770 keeps your pump, hoses, and gun protected from pressure events that can shorten equipment life.

• Restores precise bypass regulation – A worn bypass nipple changes the flow characteristics of your unloader valve. The 36311770 brings bypass flow and pressure back into spec on the ZK7.0 unloader, so the system operates the way it was designed to run.

• Prevents costly pump damage – Correct bypass operation ensures water is diverted safely when the trigger is released. That protects the pump head, high-pressure hoses, fittings, and spray gun from dangerous over-pressure conditions.

• Improves system consistency – Expect more stable pressure at the gun, fewer pressure spikes, and smoother cycling throughout your workday. Erratic pressure and bypass hose vibration are common signs that the orifice needs attention - this part eliminates those problems.

• OEM-grade durability – The nipple is constructed from brass and/or stainless steel, providing the corrosion and wear resistance needed for both cold-water and hot-water pressure washer applications, including work with common cleaning detergents.

• Quick, straightforward replacement – The 3/8" BSPP male connection threads directly into the bypass port on compatible General Pump unloaders. No special modifications, no adapter fittings, no guesswork about size or fit.

What Makes the 36311770 Different

Many generic nipples and orifice fittings can physically thread into a 3 8" bypass port, but matching the port is not the same as matching the flow characteristics the unloader valve requires for safe, consistent operation.

The General Pump 36311770 is built differently:

• Engineered for specific unloader models – This part is matched to the General Pump ZK7.0 flow-sensitive unloader valve. The orifice diameter, thread geometry, and material selection are all calibrated to ensure correct bypass balance within that valve's operating range. Installing a smaller or larger orifice from a different item number can create instability or over-pressure.

• Precision orifice sizing – The nipple has a 2.95 mm orifice diameter, tightly controlled to maintain expected GPM and PSI behavior under typical pressure-washing loads. Generic fittings often lack this level of dimensional control, which is the primary reason pressure performance degrades after a non-OEM replacement.

• Verified compatibility and performance – As a genuine General Pump product, the 36311770 is tested to work with the manufacturer's own unloader valves and pumps. That eliminates the compatibility concerns found with off-brand fittings where thread pitch, orifice bore, or material hardness may not match what the valve was designed around.

How It Works

The 36311770 bypass nipple orifice manages how much water is diverted through the bypass circuit when the unloader activates. Here is the sequence in a working pressure washer system:

1. Installed in the unloader bypass port The 3 8" BSPP nipple threads into the designated bypass port on the ZK7.0 unloader valve. The thread size of the nipple is 3/8"-19 BSPP, and the recommended tightening torque is 29.4 ft-lb (approximately 39.9 N·m), ensuring a secure metal-on-metal seal without risking thread damage.

2. Directs flow when the trigger is released When the spray gun closes, the flow-sensitive unloader opens the bypass path. The 36311770 orifice controls the volume and speed of that diverted water, preventing the sudden pressure spike that would otherwise affect pumps, hoses, and fittings.

3. Stabilizes pressure and protects components By metering bypass flow correctly, the nipple keeps the system within its rated PSI and GPM range. High-pressure systems require a primary pressure-regulating device and a secondary pressure-relief device; the bypass nipple supports the unloader's role as that primary regulator, helping the entire system continue operating safely each time the operator releases the trigger.

Product Details

Below is a quick-scan specification overview for the General Pump 36311770.

• Part number: General Pump 36311770 3/8" bypass nipple orifice

• Function: Bypass nipple with calibrated orifice for pressure-washer unloader valves; the nipple serves as a critical internal replacement part to maintain proper pressure control in the unloader valve

• Connection size and type: 3/8" BSPP (British Standard Pipe Parallel) male connection; thread size 3/8"-19 BSPP. The bypass connection measures 3/8" BSPP. Note that the inlet and outlet sizes on compatible unloader valves are both 1/2" NPT-F (NPT F outlet / NPT F bypass connections are on the valve body, not this nipple)

• Orifice diameter: 2.95 mm

• Material construction: Brass and/or stainless steel - corrosion-resistant metals suited for high-pressure water, detergents, and elevated temperatures

• Compatible unloader: General Pump ZK7.0 flow-sensitive unloader valve. The ZK7.0 unloader valve manages water bypass and reduces line pressure. General Pump unloader valves operate at 4050 PSI, with a maximum temperature of 200°F and a flow rate of 21 GPM. The unloader valve has a maximum pressure of 4050 PSI

• Installation torque: 29.4 ft-lb (≈ 39.9 N·m)

• Typical applications: This component is used in high-pressure washing systems and industrial cleaning setups, including fleet washing, facility maintenance, agriculture, and construction equipment cleaning. Commercial and industrial cleaning applications utilize high-pressure washers with the unloader mechanism

• OEM status: Genuine General Pump replacement component; the 3/8" BSPP nipple replaces ZK7.0 unloader valve parts

• Related part numbers: General Pump 36311870 nipple fits ZK7.2 unloaders (different orifice size - do not interchange)

• Included in the package: One (1) General Pump 36311770 bypass nipple orifice; unloader valve, seals, and additional fittings are sold separately

Who the General Pump 36311770 Is For

This part is designed for owners, operators, and technicians maintaining compatible General Pump unloader valves - it is not a universal fitting and should not be used as a substitute in other valve brands or unloader models.

• Professional pressure-washing contractors – Those running trailer- or truck-mounted rigs who need reliable bypass performance during long hours of daily use and cannot afford to lose time to pressure issues on the job site.

• Maintenance teams in facilities and plants – In-house crews responsible for keeping wash bays, food processing areas, or manufacturing lines clean with General Pump-powered systems where uptime and safety conditions are non-negotiable.

• Equipment rental yards and service centers – Businesses that maintain fleets of pressure washers and must replace worn unloader components with the correct OEM product to ensure each unit leaves the yard in spec.

• Technicians troubleshooting unloader issues – Service professionals diagnosing pressure spikes, overheating bypass lines, or erratic pressure that may trace back to a damaged or worn orifice nipple. If the bypass hose vibrates, pressure won't hold, or the pump heats up quickly in bypass mode, check this part first.

If the existing nipple in your unloader is stamped or documented as General Pump 36311770, this is the correct OEM replacement - choose it with confidence and add it to your cart.

Frequently Asked Questions

These answers address the most common questions about the 36311770's fit, function, and installation. Read through them before you purchase to ensure this is the right match for your system.

Which unloaders is the 36311770 compatible with? The nipple is compatible with the General Pump ZK7.0 flow-sensitive unloader valve. Always verify compatibility using your unloader model number and parts diagram before ordering. If your valve is a ZK7.2, for example, the correct part number is the General Pump 36311870 - not this item.

Is the 36311770 a universal 3/8" nipple orifice? No. While it uses a 3/8" BSPP connection, the internal orifice diameter (2.95 mm) and overall geometry are calibrated specifically for General Pump unloader assemblies. Do not assume it will work in all brands or valve types. A mismatch in orifice size can create unsafe pressure conditions or cause the unloader to lose regulation.

Can I replace this part myself? Many experienced users and technicians can replace the bypass nipple with basic hand tools. You must fully depressurize the system, follow lockout procedures, apply appropriate thread sealant (non-setting PTFE or equivalent), and tighten to the specified 29.4 ft-lb torque. If you are unsure about any step, consult a qualified service professional.

What symptoms suggest this nipple orifice needs replacement? Common signs include erratic pressure when releasing and pulling the trigger, unusual bypass hose vibration, visible wear or corrosion on the existing nipple, or difficulty keeping pressure within the expected range. If the bypass line gets hot unusually fast, that may also indicate a problem with the orifice restricting flow.

Does using OEM parts really matter? Yes. OEM components like the 36311770 are matched to the valve's internal design, helping maintain rated GPM, PSI, safety, and long service life. Generic fittings may use softer metals, imprecise orifice bores, or incorrect thread profiles - things that affect performance and can create safety risks in a high-pressure system.

How should I maintain the bypass circuit after installing this part? Regularly inspect connections for leaks, check bypass hoses for heat damage, and keep the unloader and bypass lines free of debris. Use an inlet water filter to prevent sediment from reaching the orifice. Avoid running the system in bypass mode for more than two to three minutes continuously, as recirculating water creates heat that can affect both the pump and the orifice over time.

Ready to Restore Your Unloader's Performance?

Replacing a worn bypass nipple orifice with the General Pump 36311770 is one of the fastest, most cost-effective ways to bring a compatible pressure-washing system back to stable, reliable operation. You get OEM fit, predictable bypass behavior, and better protection for your pump and accessories - without replacing the entire unloader assembly.