Technician Note
The most common spring complaint I see is no hot water after de-winterizing. Nine times out of ten the water heater bypass valves were never returned to normal position. The system filled, pressure came up, everything seemed fine — but the heater tank never got water in it. The other one I see constantly: antifreeze flushed in fall but nobody flushed it out properly in spring. Understand your bypass valves and your fixture sequence. That's most of it.
The Valve Rule — Know This First
Quarter-Turn Valve Position
Handle pointing with the line = open. Handle pointing across the line = closed. This applies to almost every quarter-turn valve in your RV water system. When you're not sure whether a valve is open or closed, look at which way the handle points relative to the pipe it's on.
This one rule prevents more winterizing and de-winterizing mistakes than anything else. Valves left in the wrong position after fall service are responsible for most spring water system problems.
Winterizing
The Full Walkthrough
Systems vary — some have dedicated winterizing ports, some don't. Some water heaters have one bypass valve, some have two or three. The principles below apply regardless of your specific setup. When in doubt, reference your owner's manual for your exact configuration.
01
Drain the fresh water tank
Open the fresh tank drain and let it empty completely before you start. You don't want fresh water diluting your antifreeze as it moves through the system.
02
Pull and drain the water filter cartridge
If your RV has an inline water filter, remove the cartridge now. Running antifreeze through a filter damages the media — and a saturated filter needs to be replaced in spring anyway. Set the housing aside open so it can drain.
03
Set the water heater bypass valves
Locate the bypass valves on the back of the water heater — accessed from inside the RV or through a storage cubby. Configurations vary: one, two, or three valves depending on setup. The goal is to stop water flowing into and out of the heater tank so antifreeze doesn't fill it. On a three-valve setup, close the top (hot) and bottom (cold) valves and open the centre bypass. Drain the water heater before bypassing — open the pressure relief valve first and hold it open while the tank drains to allow air in.
04
Set up the antifreeze supply
Locate the winterizing port — usually a valve near the water pump with one position connecting to a short hose that leads nowhere. That hose goes into your antifreeze jug. If there's no winterizing port, connect directly to the pump inlet. Use RV-specific non-toxic antifreeze rated for water systems.
05
Run antifreeze through every fixture
Turn on the water pump. Start at the fixture furthest from the pump — usually a rear bathroom or outside shower — and open each hot and cold side until pure pink antifreeze flows through. Work your way toward the pump. Cover every fixture: all faucets (hot and cold), toilets, showers, outside shower, washer hookups, and any spray ports. Don't skip any.
06
Flush antifreeze back out of the lines
After all fixtures have run pink, pull the pump hose out of the antifreeze and let it run until the pump pulls air. Then go back through all fixtures and run them briefly again. This purges antifreeze that's sitting in the lines — antifreeze left sitting can gel in cold temperatures and expand, causing damage. Don't skip this step.
07
Pour antifreeze down all drains
About half a cup down each drain — kitchen, bathroom sink, shower. This protects the P-traps from freezing. Dry P-traps will freeze and crack if there's any moisture left in them.
08
Open the low point drains
With the pump off and pressure relieved, locate and open the low point drains on the outside of the coach — typically one for hot and one for cold. Any water remaining at the lowest points in the lines will drain out here.
09
Clear the city water inlet
Go to the city water inlet on the outside of the coach. Remove the screen. With no pump pressure in the system, depress the white check valve button — it should push in easily. Any water sitting behind it will drain out right there or through the low point drains. Replace the screen.
10
Dump the holding tanks
Empty and flush both grey and black tanks before storage. Tanks stored full or partially full cause sensor fouling, odour problems, and in freezing conditions, tank damage.
On-Demand Water Heaters
RVs with tankless or on-demand water heaters — Girard, Truma Combi, Aqua-Hot — have their own specific winterization procedures that differ from standard tank heaters. The general bypass approach does not apply the same way. If your rig has one of these systems, follow the manufacturer's winterization procedure for that unit specifically.
De-Winterizing in Spring
Return Everything to Normal — In Order
De-winterizing is mostly the reverse of winterizing, but the sequence matters and a few steps get skipped more than they should.
01
Return the water heater bypass valves to normal
This is the step most people forget. Before you fill the system, make sure the bypass valves are back in the normal operating position — both supply valves open, bypass closed. If the heater stays in bypass, the tank won't fill and you'll have no hot water. Check this first, every time.
02
Return the winterizing port valve to normal
If your rig has a dedicated winterizing port, return that valve to the normal pump position so the pump draws from the fresh tank, not an empty hose.
03
Close the low point drains
Make sure both low point drains are fully closed before filling the system. An open low point drain means no pressure will build — the water just runs out on the ground.
04
Install a new water filter cartridge
Replace the filter cartridge you removed in fall. Don't reinstall the old one — it spent the winter empty and any filter media that was exposed to antifreeze should be discarded.
05
Fill and flush the system
Connect to city water or fill the fresh tank. Open all fixtures one at a time and run them until the water runs clear — no pink tint, no antifreeze smell. Flush the toilet several times. Run the outside shower. This may take more water than you expect if the system was well winterized.
06
Fill and light the water heater
Once the system is flushed and pressure is holding, fill the water heater tank before lighting it. Running a tank heater dry will damage the element. Open a hot water tap to bleed air from the tank while it fills — when water runs steadily from the tap, the tank is full.
Sanitizing the Fresh Water System
Do This at the Start of Every Season
Sanitizing removes bacteria, biofilm, and odour that builds up in the tank and lines during storage. It takes less than a day and it should be part of every spring startup before the system is used for drinking or cooking.
- Mix a solution of household bleach and water — approximately ¼ cup of bleach per 15 gallons of fresh tank capacity
- Fill the fresh tank with the bleach solution and top up with fresh water
- Run each fixture until you can smell bleach at the tap — this gets the solution into every line
- Let the solution sit in the system for at least four hours — overnight is better
- Drain completely and refill with fresh water
- Flush all fixtures again until the bleach smell is gone
- Do not use the water for drinking until you can no longer smell bleach at the taps
Water Heater Flushing
Annual Anode Rod Check and Tank Flush
Tank-style water heaters accumulate sediment and the anode rod — which protects the tank from corrosion — wears down over time. Both need attention annually. An anode rod that's gone will allow the tank to corrode from the inside out. By the time it's leaking, the damage is done.
- Drain the water heater tank annually — at winterizing is a natural time to do this
- Remove and inspect the anode rod — replace it when it's more than 75% depleted
- Flush the tank with fresh water to remove sediment before refilling
- Inspect the pressure relief valve — open it briefly to confirm it releases and reseats; replace it if it drips afterward
- Check the burner area for debris, spider webs, and wasp nests — these are a common cause of ignition problems in spring
- Tankless and on-demand heaters do not have anode rods — follow the manufacturer's specific annual maintenance procedure for those units
The Steps People Skip
The two most skipped steps in the entire water system maintenance cycle: flushing antifreeze back out of the lines after winterizing (antifreeze sitting in lines gels and expands in hard freezes), and returning the water heater bypass to normal position in spring (causes a no-hot-water complaint that looks like a heater problem but isn't). Check both every single time.