RV Water Heater Maintenance Checklist: Anode Rod, Tank Flush, and the T&P Valve

A residential water heater gets flushed maybe once a decade and nobody dies. An RV water heater is a 6- to 12-gallon tank that lives through freeze cycles, vibration at 65 mph, and whatever mineral content came out of the last campground spigot. Skip its service long enough and you get a rotten-egg smell, a tank that rusts through from the inside, or an element that scales over and quits in the middle of a trip.

The whole job is about an hour once a year. Here's the order to do it in, and the one mistake that ruins tanks.

First: does your tank even take an anode rod?

This decides everything else, and half the anode rods sold get bought by people who don't need one.

• Suburban heaters use a porcelain-lined steel tank. Steel corrodes, so Suburban gives it a sacrificial magnesium anode rod that doubles as the drain plug. It threads into the bottom front of the tank and takes a 1-1/16" socket. If you have a Suburban, an anode rod is not optional.
• Atwood heaters (now sold under Dometic) use an aluminum tank clad in steel. Aluminum passivates on its own, so there is no anode rod — the drain plug is a nylon plug on a 7/8" socket, and that's correct. Threading a magnesium rod into an Atwood doesn't protect anything; it just sets up a reaction that eats the rod in a few months and clouds your hot water.
• Tankless units (Girard, Truma AquaGo, Furrion) have no tank and no anode. Their annual service is a descale, covered below.

Open the exterior access door and read the model tag before you buy parts. If the plug in the bottom is metal and hex-headed, you have an anode; if it's white or beige plastic, you don't.

The annual drain and flush

Sediment is the real enemy. It settles over the burner flue on the tank floor, insulates the heat away from the water, and holds moisture against bare metal.

1. Kill the heat. Turn the water heater off at the switch — both the propane and the electric side — and unplug shore power if you'll be working near the element.
2. Let it cool. Two hours minimum. That tank holds 140°F water and it will scald you.
3. Depressurize. Shut off city water, turn the pump off, and open a hot tap inside until it stops running. Then lift the T&P valve lever to break the vacuum.
4. Pull the plug or rod. Expect the last gallon to come out fast and rusty. If the rod is seized, a breaker bar and patience beat an impact gun — you do not want to strip threads in a tank.
5. Flush it. A $12 curved flush wand on a garden hose, swept around the inside of the tank, will bring out sediment a straight hose stream never reaches. Keep going until the water runs clear — usually 3 to 5 minutes.
6. Reinstall. Two or three wraps of PTFE tape on the threads, snug it down, and stop. Overtightening cracks the lining on a Suburban and galls the threads on an Atwood.

Refill with the bypass valves in the normal (not bypass) position and the pump running until a hot tap runs steady with no air, then turn the heat back on. A dry element burns out in about ten seconds.

Read the anode rod before you throw it away

The rod you just pulled is a diagnostic. A new magnesium rod is roughly 3/4" thick and smooth. Replace it when it's consumed to about 3/8", badly pitted, or when the steel core wire is showing through anywhere along its length.

• Rod gone in under a year: hard water, or you're on softened water at a seasonal site. Softeners strip the calcium that would otherwise slow the reaction, and a rod can vanish in six months. Check it twice a year.
• Rotten-egg smell in the hot water only: sulfate-reducing bacteria feeding on magnesium. Switch to an aluminum/zinc rod and sanitize the tank with a quarter cup of household bleach per 15 gallons of fresh tank, run it through, and flush. Rods run $15 to $25. A Suburban tank replacement runs $700 to $1,200 installed. That's the entire argument.

The T&P valve, the pressure regulator, and the air gap

The temperature and pressure relief valve on the upper side of the tank is the safety device that keeps a runaway heater from becoming a projectile. It is rated to open around 150 psi or 210°F, and it's the one part on this list that is genuinely dangerous when neglected.

• Once a year, with the system pressurized, flip the lever and let it blow for a second. It should discharge hard and reseat dry. A valve that dribbles after reseating, or one crusted white with mineral, gets replaced — they're about $20.
• Weeping while heating usually isn't a bad valve. RV tanks are designed to hold a 2-inch air pocket at the top that absorbs thermal expansion; the water absorbs it over time and the pocket disappears. Restore it: shut off water pressure, open the T&P lever, drain a quart out the bottom, close up, repressurize.
• Check the water pressure regulator at your city water inlet. Campground pressure over 60 psi will kill T&P valves, fittings, and eventually the tank. An adjustable regulator set to 50–55 psi is $40 well spent.

The heat side: burner tube, element, and the bypass

With the access door open, look at the parts that actually make heat.

• Burner tube. Mud daubers and spiders nest in it every summer, and a partially blocked tube is the single most common no-heat call we route. Remove it, brush it out, and confirm the flame is blue with a small yellow tip. Soot streaks above the access door mean it's burning dirty right now.
• Electric element. Pull it every couple of years and look for scale. A crusted element trips the ECO high-limit or fails outright; a new one is $20 to $40.
• Bypass valves. Cycle them to bypass and back. Valves that sit in one position for years seize, and you'll find out in October when you're trying to winterize. A bypass that leaks internally is also why some rigs never get more than lukewarm water.

Tankless owners: your annual job is a descale. Circulate white vinegar or an RV descaler through the unit for 45 to 60 minutes with a small submersible pump and two hoses, then clean the cold inlet screen. Hard-water regions make that a twice-a-year job.

When to call a pro

Do it yourself up to the point where you're working on gas or 120 volts. Call someone for:

• A seized anode rod you're at risk of shearing off, or threads that have started to strip.
• Any gas smell, a flame that won't stay lit, or sooting that returns after cleaning — that's a combustion problem, not a maintenance item.
• Water in the compartment below the tank, or rust weeping from a seam. A leaking tank is replaced, not repaired.
• An electric side that trips the breaker, which usually means a shorted element and wet insulation behind it.

A mobile tech handles all of that in your site — no dumping tanks and towing to a shop. We connect owners to vetted local pros for RV water heater repair in Denver, across Phoenix, and everywhere else on our RV repair map. If your heater is already out and you want to diagnose it first, start with gas side vs. electric side.

FAQ

How often should I replace the RV water heater anode rod? Inspect it annually and replace it when it's down to about 3/8" thick or the core wire shows. On softened or hard water, check every six months.

Can I flush the tank without pulling the anode rod? No. The drain opening is the rod on a Suburban, and sediment sits on the tank floor where only that opening reaches it.

Is it normal for the relief valve to drip when the water heater runs? A brief drip as it heats often means the tank lost its air pocket — restore the pocket first. Continuous dripping, or dripping cold, means the valve is bad.

Do I need to do anything special before winter? Drain the tank completely and leave the plug out, then set the bypass valves so antifreeze goes to the lines and not into the tank.

One call, and a local pro handles it

If the anode is seized, the burner won't stay lit, or you're staring at a wet compartment floor, call 833-FIXED-RV (1-833-349-3378). A real person answers 24/7, and we connect you to a vetted, licensed, insured RV tech near you — backed by our $2,500 Workmanship Guarantee. It's free for RV owners to use.