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What is DSI Water Heater in RV? – A Detailed Explanation

Fact checked by Stephen Conklin

what is dsi water heater

Many owners of motorhomes with legacy pilot-lit gas water heaters often wonder, “What is DSI water heater?” This three-letter acronym stands for Direct Spark Ignition, a revolutionary technology for modern RVers to enjoy sleet, snow, rain, or shine hot showers.

DSI is one of the most convenient innovations, allowing RV families to lead more comfortable and convenient lives off the grid, regardless of how Mother Nature unleashes her fury. Safety is a topmost concern, and this RV water heater technology has it to a tee.

Although you already know DSI, we’re sure you want to learn what this technology means for RVers. Hence, we prepared this article to deepen your understanding of this innovation.

So, please relax and keep reading.

Table of Contents

DSI Definition


Direct, spark, and ignition are the three words comprising the DSI acronym, giving a relatively self-explanatory definition. It should also provide an instant answer to novice RV owners who wonder, “What does DSI stand for?”

Fenwal Controls, a company with more than eight decades of unparalleled commitment to creating OEM components for global brands, introduced the first DSI system to the growing RV community. Today, RVers have an extended choice from Atwood and Suburban.

So, why did Fenwal Controls invent DSI?

Tank-type gas water heaters for motorhomes are almost exclusively vehicle exterior-mounted. So, you must go outside the RV, head to the water heater, and use a lighter or matchstick to ignite the pilot light. Please note there weren’t long-barrelled barbecue stick-type lighters in that era.

Going out of your RV to ignite the pilot light shouldn’t be an issue on a sunny day. However, it becomes problematic when it rains or snows. You’ll be wet as a chick entering the motorhome after starting the pilot light.

DSI technology addresses this issue. You no longer have to go outside to light the pilot light. You simply need to flip the DSI water heater switch inside the motorhome to enjoy hot water.

Key Components and Functioning of DSI Ignition Systems

A water heater with DSI technology isn’t different from other water heating appliances. There’s a storage tank for accommodating cold water for heating. However, the system replaces a conventional pilot light. The following are a DSI system’s principal components.

1. Control Board or Module


DSI technology has a “super brain” that allows the system to “know” when to open and close the gas valve. This component also “senses” defects in the water heater ignition to ensure RVers’ safety.

The control board is a technical masterpiece comprising proprietary designs, algorithms, and integrated circuits beyond this article’s scope.

2. Igniter


It’s like an electronic lighter that delivers current to a wire to initiate a spark. Interestingly, some folks liken the system to a Piezoelectric igniter. However, it’s worth noting that the Piezo system works like a hammer to create an electrical discharge.

DSI vs. Pilot Ignition


We mentioned that DSI replaces a conventional pilot light. So, how exactly do they differ?

Pilot ignition is tedious, involving many steps. First, you have to remove the gas water heater’s access panel and turn off the gas regulator valve. Next, you must adjust the temperature control valve to its lowest setting.

The next step requires turning the gas regulator valve to the “Pilot” position. You then get a lighter or matchstick and place the flame near the pilot valve while holding the gas regulator valve down. Alternatively, you can press an igniter button.

A water heater for RV with an integrated DSI technology removes these cumbersome steps. You only need to flip a switch, and you’re off to a warm, refreshing shower.

Related tips: How to Turn on an Electric Water Heater in an RV

Benefits and Advantages of Using DSI Water Heaters


After learning about this technology, “What does DSI mean for RVers and their families?” We know this system offers many distinct advantages, among which two merits stand out.

1. More convenient

Given that DSI water heaters use a direct spark to light the gas burner, hot water can be available at a quicker rate. In addition, it saves you the trouble of having to go out of the RV to ignite the pilot light, which can be a hassle or downright dangerous in harsh weather.

2. Safer

Remember the DSI’s “super brain?” The DSI computer regulates gas flow to the burner and features built-in safety technologies.

The system only allows three attempts to light the propane gas, after which it automatically closes the gas supply. Hence, you’ll never worry about propane gas filling the motorhome’s interior and undermining your health and safety.

The DSI control board also shuts off the ignition system once its sensors detect the water in the tank is at the desired temperature. It automatically reopens if the water temperature dips or there’s insufficient water in the storage tank.

It also has a DSI fault alarm system that shows the possible existence of a problem. Examples are a control board malfunction, an open ECO circuit, an engaged check valve, absent airflow to the combustion chamber, and a possible leak.

Ignition Process and Sequence in a DSI Water Heater


DSI water heaters are hassle-free to operate, requiring only a single user action. The magic starts as soon as you flip the switch. Here’s what happens.

  • The switch activates the control board to open the gas valve and deliver electric sparks to the burner.
  • The resulting action ignites the water heater burner and continues firing until the water in the storage tank reaches the desired temperature.
  • The control board shuts off the burner, reigniting the system only when the stored hot water drops below the predetermined temperature.

Maintenance and Troubleshooting Tips

Maintaining a DSI water heater shouldn’t be different from other types. Troubleshooting is also more straightforward.

  • Ensure the gas valve is open before flipping the switch.
  • Assess the propane gas tank. The DSI system will not ignite the burner if there’s no gas in the tank.
  • Learn how to reset the DSI if you notice the fault indicator. Here are several methods of DSI resetting.

Press the reset button.

Cut off the motorhome’s power supply for 15 minutes before re-establishing power.

Close and disconnect the propane tank before reconnecting and slowly opening the gas valve.



What are the different DSI water heater types?

Contrary to what some RV owners think, DSI has two types: single-purpose and dual-purpose.

Single-purpose DSI systems only run on propane gas, while dual-purpose units operate on either gas or electricity. The latter has two switches, one for gas and another for electricity.

An excellent example of a dual-purpose DSI is Suburban’s 12-gallon SW12DEL 5248A. It features a 120-volt, 1440-watt Incoloy heating element and a 12-volt electrical heating relay. The system delivers an astonishing 16.2 GPH recovery with both gas and electric switches turned on.

What activities must I perform before turning on a DSI water heater for the first time?

DSI water heaters are similar to other types, differing only in their ignition system. Hence, RVers must ensure the storage tank contains water and that the motorhome connects to a dependable water source. Open the water heater bypass valve and power on the RV’s onboard water pump.


And there you go, a detailed answer to the mystery, “What is DSI water heater?” Your confidence is higher. Moreover, you’re ready to spread knowledge to other RVers who might still be in the dark about this water-heating technology.

In simple words, DSI is a modern component that automatically ignites and regulates a water heater’s burners to deliver a hassle-free and safe water heater experience. You don’t see the mechanism (only the switch), but knowing how it works should give you an advantage over other RVers.


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