Little Giant AX43HP / 3HTHP 120,000 BTU High Pressure Propane Water Heater Basic Starter Package
Part Number: AX43HP
The Little Giant AX43HP / 3HTHP is a 120,000 BTU high pressure propane water heater designed to boost solution temperature for truckmount carpet cleaning systems, portable extractors, pressure washing systems, tile and grout cleaning, hard surface cleaning, and restoration equipment.
This basic starter package includes the main heater components most buyers need to begin setting up a high pressure propane heater system. It is ideal when you need more heat for removing grease, oil, gum, wax, tar, and heavy traffic lane soil.
Why Choose the Little Giant AX43HP?
- 120,000 BTU propane heat for serious hot water performance
- High pressure heater design for professional cleaning systems
- Boosts heat output on truckmounts, portables, and pressure washing equipment
- Thermostatically controlled and commonly adjustable to 200°F
- Helps melt grease, gum, wax, tar, oil, and traffic lane soil
- Basic starter package includes heater, ignitor, regulator, propane hose, and pressure relief valve
Package Includes
- Little Giant 3HT / 3HTHP 120,000 BTU propane heater, high pressure model
- Little Giant spark ignitor V-1 for propane heaters
- Little Giant PR1000 pressure relief valve
- Little Giant #204-00 pressure gas regulator rated up to 140,000 BTU
- Little Giant propane gas hose
Important: This is a basic starter package, not a complete universal installation kit. Additional fittings, elbows, adapters, pressure hose, mounting hardware, propane tank, venting, and installation parts may still be required depending on your equipment and installation layout.
High Pressure Heater Information
The high pressure Little Giant heater is commonly used for higher pressure cleaning systems. The high pressure version is designed for approximately 1300–1500 PSI coil capability; however, this package includes a 1000 PSI safety relief valve. For this reason, system operation should remain under the safety relief valve rating unless a properly rated valve and complete system design are supplied by a qualified installer.
Standard Little Giant propane heaters are commonly used in lower pressure ranges and normally use a lower pressure relief valve. Always confirm the pressure rating of the heater, pump, hoses, fittings, wand, tool, and pressure relief valve before operation.
Propane Regulator and Hose Notes
The gas pressure regulator must be rated higher than the BTU demand of the heater. A regulator that is too small will reduce gas flow, reduce gas pressure at the burner, and lower hot water output.
The included Little Giant #204-00 regulator is rated up to 140,000 BTU and is commonly used for Little Giant #1, #2, and #3 Hotomatic heaters. Use a minimum 1/2" inside diameter propane hose for #1, #2, and #3 HT Hotomatic heaters. Undersized propane hose can restrict gas flow and reduce burner performance.
Water Connection Notes
- Cold water inlet: top inlet, 1/4" male pipe thread
- Hot water outlet: rear outlet where the pressure relief valve is installed
- No universal pressure hose, 90-degree elbow, or complete plumbing kit is guaranteed unless listed above
- Additional brass fittings may be needed to match your truckmount, portable extractor, pressure washer, or hose setup
Common Applications
- Truckmount carpet cleaning heat booster
- Portable extractor hot water upgrade
- Pressure washer hot water conversion
- Tile and grout cleaning
- Hard surface cleaning
- Grease, oil, tar, wax, and gum removal
- Restoration and flood cleanup support equipment
Safety Warnings
- Propane heaters must be installed and operated by a qualified person.
- Always follow local, state, fire, propane, vehicle, and insurance requirements.
- Never operate the heater without a properly installed pressure relief valve.
- Never light the burner unless the coil is completely full of water.
- Dry-firing the coil can permanently damage the heater and void warranty coverage.
- Check all propane fittings with soapy water before lighting. Bubbles indicate a leak.
- If you smell propane or rotten eggs, immediately turn off the propane tank and stop operation.
- Keep a fire extinguisher available at every service vehicle door opening.
- Route the relief valve discharge to a safe location, recovery tank, or under the service vehicle as required.
Why Buy the Starter Package Instead of Heater Only?
The heater-only version does not include the propane regulator, propane hose, ignitor, or pressure relief valve unless specifically stated. This AX43HP basic starter package saves time by including the major Little Giant heater components commonly needed for a professional installation.
Frequently Asked Questions
Is this the same as the Little Giant 3HTHP?
Yes. AX43HP is commonly used as a package or ordering reference for the Little Giant 3HT / 3HTHP high pressure 120,000 BTU propane heater setup.
Does this include a propane tank?
No. The propane cylinder or propane supply tank is not included.
Does this include every fitting needed for installation?
No. This package includes the major heater starter components, but every installation is different. You may still need elbows, adapters, solution hose, quick disconnects, mounting parts, and installation labor.
Can this be used with a truckmount?
Yes. Little Giant propane heaters are commonly used to boost solution temperature on truckmount carpet cleaning systems.
Can this be used with a portable extractor?
Yes, when the portable extractor, pump, hoses, fittings, and pressure relief system are compatible with the heater and installed correctly.
Can this be used for pressure washing?
Yes, when the pressure washer flow, pressure, fittings, hose ratings, and safety relief system are properly matched to the heater.
What pressure relief valve is included?
This basic package includes the Little Giant PR1000 1000 PSI pressure relief valve.
What happens if my system pressure exceeds the relief valve rating?
The relief valve can open and discharge hot water or steam. Always design the system so the pump pressure, heater, hoses, fittings, and relief valve are compatible.
SEO Search Terms
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Package Includes
Note the items below are not going to be all the parts you will need to set up your heater but the main parts to start with.
Important Note: It is extremely necessary that the Gas Pressure Regulator used to supply the heater with LP Gas has a capacity rating higher than the consumption of the heater. Too small a regulator will decrease the gas flow, the gas pressure and the amount of hot water produced. The Model #20400 Regulator is rated at 140,000 BTU/Hr., which is sufficiently sized to supply the gas for Models #1, #2 or #3 Hotomatic® heaters. The Model LV4403C9 Regulator is rated at 575,000 BTU/Hr., which is the model we recommend for the #4 HT Hotomatic. The top water inlet is 1/4" Mip. No pressure hose or 90 degree elbow is provided. If you need a pressure hose or brass fitting to hook up your heater, please let us know.
A gas supply hose that is too small will reduce the flow rate of the LP Gas. This reduces the gas pressure at the burner and the amount of hot water produced. Use a 1/2" I.D. Hose minimum for the #1, #2 or #3 HT Hotomatic heaters. Use a 3/4" I.D. Hose for the #4 HT Hotomatic heater.
We Have Been Making Water Heaters Since 1904. This long tradition of efficient performance is the result of rigid control of manufacturing details and the use of the finest materials and craftsmanship available. Little Giant Water Heaters have proven to be dependable under the true test of constant daily use. They will provide long, care free service and the maximum is satisfaction.
Set Up instructions
Little Giant Set Up Diagram
Little Giant Use Instructions
Operation Instructions for Hotomatic Gas Water Heaters
**********Failure to follow these instructions could result in damage to your
heater, a fire, and/or injury*************
Install fire extinguisher at every service vehicle door opening.
1. Hook heater to LP gas supply tank with certified LP gas hose with regulator. The
hookup is on the left side of the Unitrol gas valve. **Make sure the Unitrol gas
valve is in the OFF position.** You should also make sure you are not smoking,
and there are no open flames or sparks within 20 feet of the vehicle.
2. Turn on the gas on the tank and check to ensure there are no gas leaks. You can
use a spray bottle with soapy water mix to spray on the joints where your fittings
are. If you see bubbles, you have a leak.
3. Make sure the pressure relief valve is installed into the ¾” female “HOT” water
outlet on the back side of the heater. ATTENTION: Use of this heater without
a pressure relief valve voids your warranty and could cause damage to your
heater and/or result in severe injury.
4. Hook your wand into the “HOT” water outlet where the pressure relief valve is.
5. Hook the cold water supply to the ¼” male nipple at the top of the heater.
6. Turn on water, check for leaks, and double check to make sure coil is full. Failure
to do so could cause a dry-fire situation on your coil, which will ruin your heater
coil and could cause a rupture. A dry-fire is running your heater without water in
the coil, which softens the metal and voids your warranty.
7. Once the heater is full of water, you may turn the Unitrol gas valve to the
“PILOT” position to ignite the pilot flame. You will then need to push the
plunger down numerous times and hold it down on the last time to purge any air
out of the lines.
8. While holding the plunger down, you will then push the spark igniter down
numerous times until you can see the pilot flame ignite. Keep holding the plunger
down for 10-15 seconds so the pilot flame will heat up the thermocouple. You
may then release the plunger, and the pilot flame should stay on. IMPORTANT:
If the pilot flame does not light on the initial try, or goes out when you release the
plunger, wait 5 minutes so that any built up gas will dissipate and reduce the risk
of an explosion. After 5 minutes, start again at #7.
9. Once the pilot flame is lit, you may then turn the on/off/pilot valve to the “ON”
position and set the thermostat to the desired temperature range. AT THIS
POINT, DOUBLE CHECK TO MAKE SURE YOUR WATER SUPPLY IS
ON!!! The heater should then fire its main burner and heat until the desired
temperature is reached. Once the temperature is reached, the main burner will
shut off and the heater will go into a standby mode with the pilot flame still
burning. If the pilot flame should ever go out, do not attempt to relight it for at
least 5 minutes to allow dissipation of any built-up gas inside the heater.
10. If you ever smell rotten eggs, this is a sure sign you are leaking propane gas or
have a build-up of gas in the immediate area. STOP WHAT YOU ARE
DOING AND TURN THE GAS VALVE OFF ON YOUR LP TANK.
11. These heaters are designed to run 600psi max unless you have the high pressure
coil which has the capacity of 1400-1500psi max. Running a psi higher than the recommended specs for your heater, even once, can result in a coil rupture and is
NOT covered under warranty. We will know if you do, so don’t… Please note the pressure relief valve is set for 1000 psi so once you set your pressure over 1000psi steam will spray out this relieve valve! Be sure to install a hose from the relief valve discharge to your vacuum tank or under your service vehicle.
12. These heaters have the capacity of heating the water to 180+ degrees F, please
take any and all precautions to protect yourself, and your equipment, by following
these instructions.
Related Documents
Hotomatic Instructions
Hotomatic Operating Setup Diagram
Hotomatic 2HT Parts List
Hotomatic 3HT Parts List
Hotomatic H Parts Breakdown Page 1
Hotomatic H Parts Breakdown Page 2
Hotomatic HT Parts Breakdown Page 1
Hotomatic HT Parts Breakdown Page 2
Hotomatic Troubleshooting Guide Page 1
Hotomatic Troubleshooting Guide Page 2
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Optional
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Magnetic Clamp-On Water Softener Descaler for Truckmount & Portable Carpet Cleaning Machines 20260425
- Helps prevent scale buildup in pipes, coils, heaters, and carpet cleaning heat exchangers
- Reduces or eliminates routine monthly descaling in many applications
- Clamp-on installation — no cutting, plumbing, salt, chemicals, or cartridge replacement
- Maintenance-free design — no salt, resin, plastic pellets, filters, or media to flush
- Improves heat transfer efficiency by helping keep mineral buildup off heater surfaces
- May improve water flow / GPM by helping reduce mineral restriction over time
- Only 4 inches long for installation in tight areas on portable and truckmount equipment
- Longer Equipment lifespan
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