San Diego doesn’t get hard freezes. It doesn’t snow in El Cajon. The pipes don’t burst at 20°F like they might in Flagstaff or Denver. But “winterization” for a San Diego RV owner is a real and necessary process — it’s just different from what owners in colder climates face. The threats here are different: UV exposure, condensation in systems that aren’t used for months, rodent access in stored rigs, and roof sealant that dries and cracks over a mild but dry winter.
San Diego RV Center has been handling winterization and de-winterization for San Diego County owners since 1990. Here’s what the process actually involves when you’re not dealing with sub-freezing temps, and why it still matters.
The San Diego Case for Winterization
The case isn’t about frozen pipes — it’s about systems that sit idle. An RV water system that goes unused for four to six months accumulates biofilm, stale water in lines, and potential bacterial growth in the water heater. An engine that sits without being started loses battery charge, seals dry out, and fuel can degrade. A roof that goes unexamined from October through February is a roof that lets a small sealant failure become water infiltration damage by spring.
The other San Diego-specific factor: mild winters encourage complacency. An owner in Montana knows winter is coming and prepares accordingly. A San Diego owner may assume nothing bad can happen in 60-degree weather and skip the process entirely — then discovers in March that a roof leak has been running into the decking for two months. Our roof repair team sees this pattern regularly in the spring.
Water System: What to Do and What to Skip
In San Diego, a full antifreeze treatment of the water system — the standard approach in freezing climates — is typically unnecessary. What you do need to address:
Drain the fresh water tank completely. Run all faucets until no water flows. Drain the water heater — there’s a drain plug on the exterior — and leave it open so any remaining moisture can evaporate. If the rig will be stored for more than a month, add a water heater bypass and blow out the lines with low-pressure air (an air compressor with a blow-out adapter, available at most RV supply stores). This removes standing water from the lines without antifreeze, which is appropriate for San Diego’s climate.
For the grey and black tanks: flush both completely, then treat the black tank with a holding tank enzyme product to prevent residue hardening. Leave valves in the closed position during storage to prevent drying and cracking of the seals.
Roof and Exterior: A Pre-Storage Inspection
October is one of the two best times of year to do a roof inspection — before the rig sits for months, when you can identify and address any sealant failures that would allow moisture in during winter rains. San Diego does get rain between November and March, and a failing vent seal will let in water whether it’s 40°F or 70°F.
Walk the roof and check every penetration: vent flanges, skylights, AC unit seals, antenna boots, and the front and rear cap seams. Any gap, crack, or separated sealant should be addressed before storage — a failed seal gets worse over time, not better. Our roof sealing guide covers what to look for. If you find potential delamination, address it before winter, not after.
Propane and Appliance Shutdown
Close the main propane valve at the tank before storage. Propane regulators that are left under pressure for months can develop small leaks — closing at the source is a standard storage practice. Turn off the water heater’s propane supply at the appliance level as well.
For the refrigerator: empty it completely, clean it, prop the door open slightly (many have a storage latch position), and turn it off. A closed, sealed refrigerator that sits for months grows mold reliably. The same applies to any other appliances that might trap moisture — oven, microwave drawer seals. Give everything a wipe-down with a mild antimicrobial cleaner before closing up for the winter. According to RV LIFE, appliance moisture management is one of the most consistently overlooked steps in RV winter storage preparation.
Engine, Batteries, and Electrical
For motorhomes: if the rig will sit for more than 60 days without being started, consider a fuel stabilizer additive in the tank to prevent phase separation and varnishing in the fuel system. An oil change before storage — rather than after — is also worth considering, since used oil contains combustion byproducts that can corrode engine internals over a long storage period. Our motorhome oil change services are often scheduled in October by owners going into winter storage.
Batteries: disconnect or use a trickle charger rated for storage. A 12V house battery bank left unattended for six months will discharge to the point of sulfation — a form of permanent damage that significantly reduces capacity. A $30 battery maintainer plugged into shore power is considerably cheaper than replacing a battery bank. For lithium batteries, check the manufacturer’s specific storage voltage recommendations.
Pest Prevention and Cover Selection
San Diego’s mild winters are also mild for rodents, who will happily spend November through February inside your RV if you give them an entry point. Before storage, check every potential access point on the exterior underside: where pipes, wires, and hoses enter the coach. Steel wool and sealant in any gap larger than a quarter inch is effective and not expensive. Peppermint oil on cotton balls placed at potential entry points is a widely used secondary deterrent.
For a cover: if the rig is stored outdoors (which most San Diego owners do), a breathable RV cover prevents UV damage and keeps the exterior clean while allowing moisture vapor to escape. A non-breathable cover traps humidity inside and can cause more moisture problems than it prevents. Our service team regularly sees condensation damage on rigs that were covered with non-breathable tarps during storage.
A Professional Pre-Storage Check Worth Scheduling
A professional pre-storage inspection covers everything the owner walkthrough misses: roof membrane condition from up top, a full electrical system check, brake system condition, and slide-out seal integrity. San Diego RV Center serves El Cajon and all of San Diego County. Our maintenance services include a pre-storage check that addresses every system that’s going dormant for the winter. Scheduling this in October — before the holiday rush — means we can address any issues before the rig sits, rather than finding them in the spring when you’re ready to travel. Contact us to schedule your winterization service.
Frequently Asked Questions About RV Winterization in San Diego
Do I need antifreeze in my RV water system in San Diego?
Generally no — San Diego’s temperatures rarely drop low enough to freeze water lines outdoors. Draining the system, blowing out the lines, and draining the water heater is sufficient for local storage conditions. If you’re traveling to mountain areas above 4,000 feet in winter, antifreeze treatment makes sense before that trip.
How long can I store my RV without starting it or using it?
With proper preparation — fuel stabilizer, battery maintenance, water system drained, propane closed — a motorhome can sit for three to four months without significant issues. Beyond that, you’re increasing the risk of fuel system problems, battery damage, and seal deterioration. Check in on it every six to eight weeks at minimum.
When should I de-winterize my RV in the spring?
February or March, before your first planned trip. De-winterization involves reconnecting the water system, checking all appliances, testing the roof condition after winter rains, starting the generator, and charging the battery bank fully. Our maintenance team handles de-winterization as a scheduled service as well as winterization.
Is it worth paying for professional winterization in San Diego?
For owners comfortable with their rig’s systems, the DIY process described here is manageable. A professional pre-storage inspection makes the most sense when: the rig is older and more likely to have system issues, you want the roof inspected by someone who can go up top, or you don’t have a safe way to drain and blow out the water system yourself. Call us at (619) 561-3531 to discuss what makes sense for your specific rig.
Schedule Your Pre-Winter RV Inspection
October appointments fill fast. San Diego RV Center covers the full pre-storage checklist — roof, water system, electrical, engine, and appliances — so your rig comes out of storage ready to travel in the spring.
Schedule Service Now or call us at (619) 561-3531.