RV Tech — Water Systems
The Fix Most RV Techs Won't Even Think to Check
But I did! Let's try to save your vacation!
🚿🚌The Problem
It may not be the Water Heater - Many factors are critical to tankless water heaters.
If your RV's tankless water heater is shutting off randomly, or if the water never quite gets warm, or it gets warm then suddenly the temperatures drop. There's a good chance nothing is broken. The heater is doing exactly what it's designed to do, but something else is wrong. Possibly water flow.
Tankless heaters are fundamentally different from the tank-style units most RVers grew up with. They don't store hot water. They heat water as it moves through the unit. Cold water coming in (made worse in winter conditions) may require you to lower flow found on the water heater itself, will need to be adjusted. But this combined with other restrictions can be too much. Triggering unusual behavior. It's all about balance. Especially when you are transitioning from season to season. Shoulder months are difficult.
Get the flow wrong in either direction (too much or too little) and you'll have problems. Too much flow, and the heater can't keep up with the volume — you'll never reach your target temperature. Too little, and the unit's internal flow sensor won't detect enough flow to activate the burner. Or, it will start then randomly shut off. No error code. No warning. Just cold water.
Inside a tankless water heater is a flow sensor — typically a small turbine. When water moves through it, the sensor signals the burner to ignite. If the flow slows, and the unit cuts out. Too much water and you just get a tepid, uninspiring shower.
Common Misconception
You Can't Use a Tankless Heater Like a Tanked One
This is the single biggest mistake I see.
With an old tank-style heater, the standard approach is to set the unit to a high temperature, then blend in cold water at the faucet or shower valve to reach a comfortable temperature. That works fine with a tank. This is also why so many traditional RV water heaters seem so hot -- they are stretching the 6 gallon tank farther by having you 'cut' the hot with cold water. Its a clever solution - but it can be a scald risk. That is another tech-tip.
The right approach with tankless: set the heater's output temperature to a comfortable, desired heat. Never mixing cold and hot to find the sweet spot. Rely only on the digital control panel. Let the heater do the temperature work. The hot valve is just for flow and the cold isn't used at all.
Tank-Style Heater
- Stores a reservoir of hot water
- Set high, blend cold at the tap
- Flow rate doesn't affect operation
- Works fine at any trickle
- Heats water even when idle
Tankless Heater
- Heats water only when it's flowing
- Set to a comfortable temp — don't mix cold
- Requires minimum flow to stay activated
- Low-flow fixtures can shut it down
- Only uses energy when you're using water
A possible repair for inconsistent water, or water that just goes cold
Why was my customer taking cold showers?
Here's a scenario. The customer reports their tankless water heater is shutting off randomly during showers — no pattern, no error code, no obvious cause. Everything else in the rig is working fine. But while showering the water would just turn cold.
After checking the basics (propane, water pressure and flow from the campground it all looked fine.
the culprit turned out to be the bathroom shower head. Originally designed for a tanked heater, it was installed with a low-flow water restrictor — a small plastic insert designed to save water. In a standard plumbing setup, these are common and sometimes required. But, with a tankless water heater, they can quietly cause havoc.
That restrictor was dropping the shower's flow rate close to or below the heater's minimum activation threshold. The heater would sense flow, fire the burner, start heating — then the sensor would not see sufficient flow and cut out. Over and over. The result felt like a random, intermittent shutdown. But the unit was behaving exactly as designed.
The key to this was that the kitchen sink never has this problem. It used more water than the shower, and the heater had time to get to full operating temperature and keep running.
The fix? A dental pick and 5 minutes.
Not all shower heads are built the same. Some have the restrictor at the inlet connection (the threaded end that screws onto the hose). Others have it deeper in the head body. Some premium or brand-specific models don't have a removable restrictor at all. Check your specific model before assuming it's a simple pop-out fix. Then there is the water heater itself. It needs propane, water pressure (PSI), and gallons per minute available on the input side. If you have very low pressure from the campground or city, this may be an issue as well.
As a test, you can use your on board water pump! Fill the fresh tank, and use the pump instead of city water. Those should be adequate even if the camp water isn't - it's a nice backup if you find low city water pressure.
DIY Guide
How to Remove a Flow Restrictor from an RV Shower Head
This is one of the most DIY-friendly fixes in RV plumbing. No special tools. No prior knowledge required. Most of the time you need about 5 minutes and something small and pointy. I use a metal pick similar to what a dentist would use. I got my set from an auto-parts store.
Step-by-Step: Shower Head Restrictor Removal
If your water heater or RV is still under manufacturer or dealer warranty, do not attempt any modifications — First consulting your dealer or the manufacturer. It's better to be safe than sorry. When in doubt, always call a pro first.
Know Your Limits
Who Should DIY — And Who Should Call a Tech
The shower head restrictor removal described above is genuinely beginner-friendly. If you've ever assembled flat-pack furniture or changed an air filter, you can handle it.
Where things get more involved is if this doesn't fix the problem. Why the flow is insufficient in the first place, or is this even the problem. A pro can help with that. A restrictor is just one cause. But clogged water filters, partially closed supply valves, internal scale buildup - in the heater any of these can produce the same symptoms. If removing the restrictor doesn't fix it, there's more going on — and that's when a tech is worth every penny. Just tell him (or her) what you did. Don't hide it.
If you smell gas near the unit, or if it's making noises it wasn't making before. Don't guess on those. Call someone qualified immediately.
Before pulling anything apart, try this: turn on a second hot water tap elsewhere in the RV while showering. If the heater stays on more reliably with higher combined flow, you've confirmed the problem is flow-related — not ignition, gas supply, or an electrical fault. That narrows your diagnosis considerably before you touch a single fitting.
Still Having Trouble? That's What I'm Here For.
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Just contact us, and we’ll take care of the rest.
