INSTASHOWER ULTRA
66K BTU RV Tankless Water Heater with Mixing Tank
$899.99
FINAL ROUND DISCOUNT
$220 off with code Victory220
Enter the code at checkout. Cannot be combined with other offers.
Victory220
Stable hot water from low-flow startup to a full shower.
InstaShower Ultra combines 66,000 BTU heating, flow up to 3.9 GPM and a built-in mixing tank designed to reduce cold-water shock. Segmented combustion helps hold the selected temperature within ±1°F, while the weather-resistant system operates at elevations up to 9,800 ft.
View all features ↓66,000 BTUHigh-output propane water heating
Up to 3.9 GPMFlow for showers and daily use
±1°FTemperature stability target
0.5 GPMLow-flow burner activation
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30-day returns
Free local shipping
2-year warranty
At a glance
- 66,000 BTU heatingSupports hot-water flow up to 3.9 GPM for showers and everyday RV use.
- Built-in mixing tankBuffers the first water leaving the heater to reduce the cold-water shock common at startup.
- ±1°F temperature controlSegmented combustion adjusts flame output as water demand and inlet conditions change.
- 0.5 GPM low-flow startupActivates with lower water demand instead of requiring a high-flow shower setting.
- Weather and altitude readyHydroShield-Tech, wind resistance and operation up to 9,800 ft support varied travel.
- Three replacement door sizesChoose the opening that matches common 4/6, 6 or 10/12/16-gallon tank heaters.
Fit and installation
- Fuel
- LP propane
- Electrical supply
- 12V DC
- Door options
- 15×15 / 15×18 / 18×18 in
- Set temperature
- 95–123°F
- Pressure relief valve
- 150 PSI included
- Controller distance
- Up to 6.6 ft
Before ordering, measure the existing cutout and door, then confirm propane, 12V power, cold-water inlet, hot-water outlet and venting requirements. Professional installation is recommended.
What’s included
- InstaShower Ultra tankless water heater
- Selected gray access door and trim ring
- Smart wired controller
- 150 PSI pressure relief valve
- Installation hardware and user manual
Gas, water and electrical connection materials vary by RV and may need to be supplied by the installer.
Specifications
- Heat input
- 66,000 BTU
- Water flow
- 0.5–3.9 GPM
- Temperature range
- 95–123°F
- Temperature fluctuation
- ±1°F
- Fuel type
- LP propane
- Electrical supply
- 12V DC
- Maximum altitude
- 9,800 ft
- Weather system
- HydroShield-Tech
- Model
- FS10B1SGD
- Door color
- Gray
Common questions
How do I choose the door size?
Measure the current opening and access door. The three options correspond to common 4/6-gallon, 6-gallon and 10/12/16-gallon tank-water-heater replacements.
What does the mixing tank do?
It buffers and blends water inside the unit to reduce the brief cold-water interruption that can occur when an RV shower is stopped and restarted.
Will it work at low water flow?
It is designed to activate at approximately 0.5 GPM, provided the plumbing pressure and installation meet the manual requirements.
Does it need 120V power?
No. The controls and ignition use 12V DC; the burner uses LP propane.
Recommended for your RV setup
Pair the water-heater upgrade with climate equipment that matches how your RV is built. Confirm roof or duct requirements before ordering.
Add quiet rooftop cooling and heat-pump warmth for milder weather. Confirm a standard non-ducted roof opening, roof thickness and 115V power before ordering.
Check roof fit and options
Add stronger propane heat through the RV duct system. Confirm cabinet space, central ductwork, 12V power and LP supply before ordering.
Check furnace fit and options
InstaShower Ultra
$220 off
·
$899.99
The mixing tank and burner work together to reduce shower temperature swings.
InstaShower Ultra does more than raise the maximum flow rate. The built-in mixing tank buffers startup water, while segmented combustion adjusts flame output as demand and inlet conditions change.
BUILT-IN MIXING TANK
Less cold-water shock when the shower is stopped and restarted.
The internal pre-mix system blends water before it leaves the heater, reducing the brief cold interruption that can occur in an RV plumbing loop.
- System
- Pre-mix tank
- Target
- Smoother restart
SEGMENTED COMBUSTION
The burner changes its flame pattern instead of applying full heat all year.
Two flame rows can reduce summer overheating, while all five rows provide the heat required in colder inlet-water conditions.
- Heat input
- 66,000 BTU
- Control
- Seasonal flame stages
FLOW + STABILITY
Up to 3.9 GPM with a ±1°F temperature-control target.
The available flow supports a full RV shower and other everyday hot-water use. Actual delivery depends on inlet-water temperature, propane supply, plumbing pressure and the selected temperature.
Choose the door around the opening already in the RV.
The three door options are intended for common tank-heater replacement sizes. Measure the cutout and exterior door before selecting a variant, then confirm propane, water, 12V power and venting.
HEATER + ACCESS DOOR
A complete tankless replacement package.
The selected gray door, trim ring and controller are designed to finish the exterior opening and bring temperature control inside the RV.
DOOR SELECTION
Three common replacement sizes.
- 4/6 gallon
- 15 × 15 in square
- 6 gallon
- 15 × 18 in rectangle
- 10/12/16 gallon
- 18 × 18 in square
- Electrical
- 12V DC
Choose the water heater around flow, stability and replacement size.
8 Plus is the value-focused 55K model. 9 Pro adds 66K output and a buffered tank. Ultra raises maximum flow to 3.9 GPM and adds the most weather-focused package.
Swipe to compare →
InstaShower 8 Plus
For midsize RVs that need a straightforward tankless replacement without a mixing tank.
- Heat input
- 55,000 BTU
- Max flow
- 2.9 GPM
- Mixing tank
- No
InstaShower 9 Pro
For larger RV households that want 66K output and buffered temperature control.
- Heat input
- 66,000 BTU
- Flow
- 0.8–3.6 GPM
- Mixing tank
- Yes
InstaShower Ultra
For owners who want the highest flow, low-flow startup and broader travel conditions.
- Heat input
- 66,000 BTU
- Flow
- 0.5–3.9 GPM
- Altitude
- Up to 9,800 ft
See the heater opened, installed and tested.
These videos show internal construction, replacement work, startup and real hot-water operation outside a product studio.
Swipe to watch →
▶Inside the Ultra before installation
A bench test and internal look at the mixing tank, burner and service layout.
▶From unboxing to first hot water
Door fit, plumbing, propane, wiring and startup in an RV replacement project.
▶A second replacement example
Another installation approach that helps owners understand access, sealing and connection work.
▶Why the mixing tank matters in real use
An owner review focused on cold spots, shower consistency and off-grid hot-water performance.
▶A complete replacement and startup walkthrough
A detailed installation guide covering removal, mounting, utility connections and first hot water.
Common replacement and hot-water questions.
The buy box contains the main specifications. These answers add context for door sizing, flow, propane and winter use.
How do I choose the correct door size?
Measure the existing exterior opening and door. The 15 × 15-inch square, 15 × 18-inch rectangle and 18 × 18-inch square options correspond to common tank-heater replacement sizes.
What does the built-in mixing tank do?
It buffers and blends water before delivery to reduce the cold-water shock that can happen when a shower is paused and restarted.
Will the heater deliver 3.9 GPM in every RV?
3.9 GPM is the maximum. Actual flow depends on inlet-water temperature, the requested temperature rise, plumbing pressure, propane supply and altitude.
How low can the flow be before the burner starts?
The unit is designed for startup at approximately 0.5 GPM when the water pressure and installation meet the manual requirements.
Does it need shore power?
No 120V shore-power connection is required for the heater controls. It uses 12V DC for electronics and ignition and LP propane for heat.
Can it operate at high altitude?
It is designed for operation up to 9,800 feet, but correct propane pressure, venting and installation remain essential.
What should be winterized?
Drain the water heater and connected plumbing according to the manual before freezing conditions. Freeze protection does not replace proper winterization when the RV is stored or unpowered.
Can I install it myself?
Experienced RV owners may do so, but the work involves propane, 12V wiring, water plumbing, exterior sealing and venting. Professional installation is recommended if any step is unfamiliar.
This product is rated 5.0 of 5.0 stars.
It has received 25 reviews.
FOGATTI Blog
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