RV water heater anode rod and flush: Which heater has one
An anode rod is a sacrificial part, and whether your heater has one is decided by the metal its tank is made from. Suburban builds porcelain-lined steel tanks and fits a rod. Atwood and Dometic build aluminum tanks that take a drain plug, and Dometic's manual states that a rod fitted there damages the coupling. This covers which heater is which, the part numbers, and the flush both tanks need.
By OriginRV. Last reviewed on Nov 2, 2026.
Does your heater have an anode rod?
An anode rod is a sacrificial part. It corrodes so the tank does not, and it is meant to be consumed and replaced. Whether a heater has one is decided by the metal its tank is made from, and both kinds of tank are common on the road.
| Heater | Tank | Anode rod |
|---|---|---|
| Suburban | porcelain-lined steel, a glass lining fused to the steel tank | yes. 233514 magnesium or 233516 aluminum, and the rod doubles as the drain |
| Atwood or Dometic | aluminum with a thin clad layer over it | no, and one must not be fitted. The opening takes a drain plug |
Suburban's catalogue describes its tank as porcelain-lined steel and its glass-fused-to-steel process as comparable to a residential water heater tank. Dometic builds the heaters that were sold under the Atwood name, and describes its tank as high strength aluminum with a thin clad layer of aluminum and zinc fused over the core, and says that layer is anodic to heavy metals and acts much like an anode in a steel glass-lined tank. The aluminum tank is already doing for itself what a rod does in a steel one.
How to tell which heater you have
The name is on the data plate, on the heater itself behind the outside access door. The two heaters also look different at the point where the tank drains, and that is the check when the plate is gone.
A Suburban's drain fitting is the anode rod itself, with a hex head that a socket fits, and the whole rod comes out with it. An Atwood or Dometic has a plain drain plug, and there is nothing behind it. The anode rod finder walks through those two questions and returns the part number, or the answer that there is nothing to buy.
The Suburban rod: Two part numbers and a yearly change
233514 is the magnesium rod and 233516 is the aluminum one. Suburban's 2025 catalogue lists both as extended life anode rods, and Suburban's own accessory page lists the magnesium rod as the replacement for its tank water heaters with the aluminum one available beside it. Both fit the same 3/4 inch port, and the old rod comes out with a 1-1/16 inch socket, which is the size Suburban's operation guide gives.
Suburban gives two ways to decide when the rod is finished. The simple one is yearly: the rod will deteriorate under normal use, and because of that the guide recommends replacement every year. The measured one is wear: replacement is recommended when consumption or weight loss is greater than 75 percent. Water with high levels of iron or sulfate increases the rate of deterioration, so a heater on hard water can eat a rod well inside a year, and Suburban notes that draining the tank whenever the RV is not being used extends the rod's life.
Two consequences are stated plainly in the same manual. Operating the water heater without the anode voids Suburban's limited warranty, and the replacement should be a Suburban part: Suburban warns against fitting a non-Suburban accessory in the rod's place, such as an add-on electric heating element, because those parts are not approved for its heaters.
Suburban also names the product that goes on the threads. A pipe thread sealant approved for potable water, such as Teflon tape, must be applied to the threads of the anode rod, and the guide notes that a correctly applied sealant does not interfere with the rod's protection of the tank.
Why an aluminum tank must not be given a rod
The mistake is easy to make, because an anode rod is a cheap part, it is stocked everywhere, and it looks like maintenance. Dometic's manual for its XT water heaters states that replacing the Dometic drain plug with an anode rod will damage the coupling with cathodic action, and that product damage will result. The same manual, and the manual for the 9 gallon gas and electric model, list aftermarket anode devices alongside aftermarket heating elements as not compatible with its water heaters, and state that using them voids the warranty.
So on an Atwood or Dometic the answer is nothing to buy. The maintenance that tank actually wants is the flush, which Dometic publishes both a procedure and a schedule for.
Flushing the tank, and why it is the other half of the job
Sediment is what collects at the bottom of either tank, and Suburban describes what it does to a steel tank: sediment on the bottom forms a layer of insulation between the burner and the water, it slows heat transfer, and it overheats the tank bottom, which weakens the steel and damages the glass lining. The same sediment is what Dometic's procedure is written to clear.
The procedure is the same on both heaters, and it starts at the fitting the tank drains from.
- Turn the water off and let the heater cool. Dometic's caution is explicit about the order: turn the water heater off, allow time for the water to cool, then remove the drain plug. On a Suburban, remove the anode rod.
- Drain the tank. If the water comes out in a trickle rather than a steady stream, open the temperature and pressure relief valve to let air into the tank, then clear the drain opening with a small gauge wire or a coat hanger, which is the method Dometic gives.
- Expect about two quarts to stay behind. Because of where the fitting sits, roughly two quarts of water remain in the bottom of the tank, and Dometic states that this water contains most of the harmful corrosive particles.
- Stir those two quarts loose with a wand. Dometic recommends a commercially available water heater flushing tool rather than running water straight through the inlet, and explains why: a straight flow does not stir up the sediment. The wand lets you move around inside the tank at different angles and push the material back out of the drain opening.
- Keep going until the water runs clear. That is the finish line Dometic gives, and it is a better test than a count of minutes.
Dometic also publishes how often: a full-time RVer flushes every 60 days, and a part-time RVer at least twice a year, with both figures shortened in the Southwest, to every 30 days for a full-timer and every 90 days for a part-timer. On a Suburban the flush happens whenever the rod comes out, which is why the annual rod change is the natural moment for it.
What the rod does not fix
A rod protects the tank and nothing else. It has no bearing on a heater that will not light, will not heat on electric, or runs out of hot water, and replacing a rod will not change the temperature of the water at the tap. If the heater is not heating, the water heater troubleshooting guide works through the fault in order.
Rotten-egg hot water is the one complaint that does touch the rod, and both makers treat it as water chemistry rather than a failed part. Dometic describes hydrogen sulfide forming when the clad layer of the tank releases hydrogen from the water, and its remedy is a flush with a vinegar solution rather than a new part. Suburban's remedy is chlorination of the water system with household bleach, and the causes it names include a rod that has degraded too far or a rod of the wrong material for that water supply.
The drain plug on an aluminum tank
The plug is the part that is removed every time the tank is drained, and it is the one part on these heaters that wears out from being handled. If it is cracked or its threads are damaged, it needs replacing rather than reusing, and Dometic's own route to the number is the parts lookup on its website by the model number on the unit. The manual prints no part number for the plug itself.
Winterizing an aluminum tank does not require removing anything permanently. Dometic's instruction is to drain the tank, which leaves roughly two quarts in the bottom, and the manual states plainly that those two quarts will not damage the tank if they freeze. A Suburban has the extra step: for winter storage Suburban says to remove the anode rod, keep it for the season, and fit a 3/4 inch drain plug in its place.
Related guides
The faults a rod does not cause are in water heater not heating. Before the first freeze, winterizing the plumbing covers the system the heater sits in.
How do I know if my RV water heater has an anode rod?
The brand decides it. Suburban builds porcelain-lined steel tanks and fits a sacrificial rod. Atwood and Dometic, now both Dometic, build aluminum tanks that take a drain plug and no rod. If the data plate is gone, the drain fitting tells you: a hex-headed rod that unscrews and comes out long is a Suburban, and a short plug with nothing behind it is an aluminum tank.
How often should the anode rod be replaced?
Suburban recommends yearly, and gives a wear figure alongside it: replacement is recommended when consumption or weight loss is greater than 75 percent. Water high in iron or sulfate eats a rod faster, so a heater on hard water can need one sooner than the calendar says.
Can I fit an anode rod to an Atwood or Dometic water heater?
No. Dometic states that replacing its drain plug with an anode rod damages the coupling with cathodic action, and that aftermarket anode devices are not compatible with its water heaters and void the warranty. The aluminum tank protects itself with its own clad layer.
Where is the anode rod, and what takes it out?
On a Suburban it is at the front of the heater, and it is the fitting the tank drains from. Suburban's guide gives a 1-1/16 inch socket for it. A pipe thread sealant approved for potable water goes on the threads of the new rod.
Does the anode rod have to come out to winterize?
On a Suburban, yes, if the system is being winterized with antifreeze and there is no bypass kit: Suburban's instruction is to remove the rod, store it for the season, and fit a 3/4 inch drain plug in its place. On an Atwood or Dometic the tank is drained through the drain plug, and the roughly two quarts left in the bottom will not damage the tank if they freeze.
Sources
- Suburban, tank water heaters operation and maintenance guide, part 206244: the yearly replacement recommendation, the consumption or weight loss rule at 75 percent, faster deterioration on water high in iron or sulfate, the 1-1/16 inch socket, the pipe thread sealant for potable water, the warranty statement about operating without the anode, the warning against non-Suburban accessories, the sediment and tank-life description, the winterizing instruction that replaces the rod with a 3/4 inch drain plug, and the chlorination treatment for odor
- Suburban, 2025 catalogue SUB-401.02: the porcelain-lined steel tank series and the glass-fused-to-steel process, and the two extended life anode rods, 233514 in magnesium and 233516 in aluminum
- Suburban, replacement anode rod: the magnesium rod as the replacement for Suburban tank water heaters, with the aluminum rod available
- Dometic, L.P. gas water heater, 6 and 10 gallon XT models: the aluminum tank and its clad layer, the warning, in the maker's words, that replacing the drain plug with an anode rod "will damage the coupling with cathodic action and product damage will result", the warranty statement about aftermarket anode devices, the flushing procedure, the flushing tool, the two quarts left in the tank, the maintenance intervals for full-time and part-time use, and the vinegar treatment for hydrogen sulfide
- Dometic, L.P. gas water heater, 9 gallon gas and electric: the warning against anode rods and other non-approved devices, and the drain and cool sequence before the plug comes out
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