Oct 24th 2026
How to Winterize an RV Water Heater (Suburban, Atwood/Dometic and Tankless)
HOW-TO · WINTERIZING
How to Winterize an RV Water Heater (Suburban, Atwood/Dometic and Tankless)
Drain it, bypass it, and keep antifreeze out of the tank. Here are the steps from Suburban, Atwood/Dometic, Girard and Suburban tankless manuals.
The short version
- Turn off gas and electric first. Never run an element in an empty tank.
- Drain the tank and put the bypass valve in bypass before pumping antifreeze, so it doesn’t fill the tank.
- Suburban: antifreeze is corrosive to the anode. Pull the anode for winter and install a 3/4 in. drain plug.
- Tankless: drain or blow out per the model (no bypass needed on Girard).
Suburban tank heaters
STEP 1
Shut everything off
Turn off the electric switch or breaker and the gas. Turn off the water pump. Let the water cool.
STEP 2
Relieve pressure and drain
Open hot and cold faucets. Remove the anode rod (1-1/16 in. socket) and let the tank drain.
STEP 3
Bypass and store the anode
If you have a bypass kit, close off the heater and leave it in bypass, especially when adding antifreeze. Suburban says don’t reconnect it until spring. No bypass? Leave the anode out and install a 3/4 in. drain plug.
STEP 4
In spring: fill before heat
Reinstall the anode with thread sealant, take the heater out of bypass, and fill the tank until water runs from the hot faucets with no air before you light it or turn on electric.
Suburban winterizing parts
Atwood / Dometic tank heaters
STEP 1
Shut off and cool
Turn off gas, electric and the water supply.
STEP 2
Open the relief valve and pull the plug
Lift the P/T valve handle, then remove the drain plug. If it drains slowly, the relief valve lets air in; clear the drain opening with a thin wire if needed.
STEP 3
Flush and close up
Flush with water or air, reinstall the plug and close the P/T valve. About 2 quarts stay in the tank; Dometic says that won’t damage it if it freezes. Bypass the heater before adding antifreeze to the RV’s plumbing.
Atwood drain plug
Use the plastic plug, never a metal one or an anode.
Tankless heaters
- Girard GSWH-2: drain by opening each tap and blow out with air, or run non-toxic antifreeze through every tap. Girard says the small amount of water in the heat exchanger doesn’t need a bypass kit.
- Suburban IW60 / IW60RL: power, gas and pump off, open faucets, remove the service panel and open the red drain valve (IW60RL: also turn the black handle 1/4 turn). Antifreeze only if your RV maker recommends it.
- Suburban ST-42 / ST-60: compressed air is preferred, 40 psi max, using bypass tees and shutoffs.
- Freeze protection isn’t winterizing: tankless freeze protection only works with gas and 12V on, and only protects the heater, not your plumbing.
IW60 drain parts
Parts for this repair
Suburban 233514 Magnesium Anode Rod (SW series)View part →
Suburban 233516 Aluminum Anode Rod (SW series)View part →
Dometic/Atwood 91857 Drain Plug, 1/2 in. NPT (2 pack)View part →
Suburban 172022 IW60 Drain Valve (red knob)View part →
Suburban 172025 IW60 Frost Protection Drain TubingView part →Shop by category: Suburban parts, Dometic parts.
FAQ
Should I put antifreeze in my RV water heater?
No. Bypass the tank. Suburban warns antifreeze corrodes the anode; antifreeze in the tank is also wasted.
Do I need to remove the anode rod to winterize a Suburban?
Yes, to drain it. Suburban suggests storing the anode and installing a 3/4 in. drain plug for winter.
Does an Atwood water heater need to be completely dry?
No. Dometic says the roughly 2 quarts left after draining won’t damage the tank if it freezes.
Does a tankless RV water heater need a bypass?
Girard says its GSWH-2 doesn’t. Suburban ST models use bypass tees for blowing out with air.
Not sure which part fits? Contact us with your model and serial number from the data plate and we’ll confirm it before you order.
From Suburban tank and tankless operation guides and service manual, Dometic/Atwood installation manuals and the Girard GSWH-2 owner’s manual.