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Before you start modifying your RV water system, you need to understand how it works. Whether you’re planning to upgrade to a tankless water heater, install a water filtration system, or just troubleshoot a leak, this guide will give you the foundation you need.
Of all the systems in modern RVs, the plumbing is what truly makes it feel like home. Indoor plumbing was a MAJOR factor when my wife and I bought our first camper back in 2004 – a Casita Spirit Deluxe. Since then, I’ve worked on plumbing systems in multiple rigs including our Arctic Fox 27-5L and now our Renegade Verona motorhome.
The good news? RV plumbing is similar to residential systems, just with a few added components that make it work on the road.
The Two Main RV Water Systems
At the highest level, there are two major systems you need to understand:
- Fresh Water System – How clean water gets to your faucets and shower
- Waste Water System – Where it goes after you use it
Let’s break down each one.
Fresh Water System
You’ll get fresh water in one of two ways when camping:
Option 1: Fresh Water Tank
Your RV has an onboard fresh water tank (typically 30-80 gallons depending on rig, with some as small as 5 and some over 200 gallons). You fill this tank via hose, either through the city water connection or through a dedicated gravity fill port on the exterior. Some rigs can be filled both ways.
Pro tip: If your rig has a gravity fill port, this Camco fill adapter makes filling WAY easier than trying to hold a hose in the hole. There are brass ones on the market, but I’ve used the same one of these as long as I’ve been RVing.
Once you have water in the tank, you turn on the water pump to pressurize your plumbing system. In most RVs you can clearly hear the pump when it runs – it has a pressure sensor and only kicks on when there’s demand for water.
IMPORTANT: If your pump runs when nobody is using water, you almost certainly have a leak that needs to be found and fixed! Most common cause is the 1-way check valve built into the pump. It allows water to drain back into the tank so it isn’t damaging but just annoying. I put a shark bite 1-way valve to fix this…make sure you put it on the input side of the pump.
Option 2: City Water Connection
This is the connection where you hook your hose directly to a shore water supply.
When connected to city water:
- You don’t need to run the water pump
- You don’t even need water in your fresh tank
- The pressure comes directly from the source
This is where you need to be careful! I’ve been in campgrounds where I’d open the spigot just to test it and water would shoot out with enough force to scare me. City water pressure can vary wildly from 20 PSI to over 100 PSI.
Critical Equipment: Water Pressure Regulator
You MUST use a pressure regulator. High pressure can damage your plumbing, burst hoses, or blow out seals.
Many dealers give you cheap brass regulators as part of your “RV kit.” I don’t trust them – they severely restrict flow and I’m not convinced they regulate pressure consistently.
This Renator adjustable regulator has worked well for me for years. I had a similar one before where the gauge leaked its oil and quit working, but the Renator has been solid. Hook this either directly to the spigot or through a splitter. I want the regulator first in line so that my water hose and filter are protected from high pressure.
I run mine at 50(ish) PSI.
Other Essential Gear
For problem spigots: A couple times I’ve been in campgrounds where the spigot threads were so messed up I couldn’t get my hose to seal properly. This Camco Water Bandit has saved me in those situations.
For chlorine issues: We stayed at a campground in Moab, UT that had so much chlorine in the water it stank up the inside of our trailer. It was STRONG. After that I started carrying a Camco inline water filter. Then as an Amazon Vine reviewer this thing popped on my list and I really like it….it’s a knock off of a major brand and does a lot better job of cleaning up the water with 3 stages.
Water hose upgrade: For years we used the standard white “RV-safe” water hoses you can find anywhere. Then we discovered Zero-G hoses. These are game-changers – I can carry 100 feet of hose in the space that 30 feet of traditional hose would take. WAY less bulky and much easier to work with. The Renegade has a built in hose on a power reel, but I still carry 100′ of this and have had to use it a couple of time to get water.
Hot Water System
Most RVs come with a hot water heater, traditionally tank-based units ranging from 6 to 12 gallons. You’re now seeing more tankless “on-demand” water heaters in newer rigs.
Most water heaters can run on either:
- Propane – Works anywhere
- 110V AC power – When you have shore power or generator
Some older units have a pilot light on the gas side, but most modern systems use DSI (Direct Spark Ignition) that runs off your 12V system.
CRITICAL: Always make sure the tank has water before turning on the hot water heater. Running it dry will damage it and could be dangerous.
Quick tip: If my wife and I are both going to shower, I’ll turn on BOTH the propane and AC heating elements to speed up recovery time. We’ve always had enough hot water for comfortable showers this way.
Waste Water System
The waste water system in most RVs consists of a combination of grey and black tanks. Depending on your floorplan, you may have multiple grey tanks. In our Arctic Fox we had 1 black tank and 2 grey tanks.
- Black Tank – Toilet wastewater
- Grey Tank – Sink and shower wastewater
About tank level gauges: The factory ones are NOTORIOUSLY inaccurate. The fresh tank gauge usually works well enough since it doesn’t get gunked up with paper and other contaminants. Some people upgrade to the SeeLevel monitoring system. I resisted this for a long time, but for various reasons it has become more urgent so that will be a “comming soon” mod I’ll post about.
Important rule: Always leave the valves CLOSED when you’re at a campground with sewer hookup. Try to get your black tank half full so it dumps properly, and you want available grey water to “flush” the sewer hose after you dump the black tank.
The Dumping Process (It’s Not as Bad as You Think)
I know the first time I went to dump waste tanks I was pretty nervous. The thought of a mistake and the potential nastiness made me approach it with extreme caution. But it’s really straightforward once you understand the process.
My dumping kit essentials:
- Harbor Freight nitrile gloves (box of 100)
- Hand sanitizer
- Quality sewer hose and fittings (more on this below)
My Equipment Setup
Camper-side valve: I use a Camco gate valve that stays connected to the rig. The valve is super handy because there’s almost always a bit of water that collects in the pipe as you go down the road. With just the cap that came with the RV, that bit of water always spills on the ground when you connect. The other key feature is the clear section – this lets you see what’s backed up behind the valve before you open it.
45-degree clear elbow: This smooths the flow when you’re dumping and large amounts of water are flowing through. It prevents the violent turbulence you get with a 90-degree turn.
In the Renegade the clear elbow doesn’t really work, but I what does make it much easier is a Compartment Hose. Stays connected inside the compartment and drops out a opening in the bottom when parked. Then the rest is the same out to the dump.
Hose support: I prefer the Valterra supports over Camco because of the rubber straps that hold the hose in place. But recently I’ve been using this Kohree hose holder and like it for the most part. As you’re setting this up, think about the forces that large amounts of water will create – especially where there are curves. The hose can literally hop off cheap supports.
Sewer hose: I’ve used both the RhinoFLEX and RhinoEXTREME. The EXTREME is crush-resistant and more expensive, but honestly the RhinoFLEX is better. The EXTREME doesn’t collapse as well and is harder to work with. I made the mistake of thinking “more expensive must be better.” The RhinoFLEX is the solid choice – it typically lasts me 3-4 years.
Universal adapter: Keep one of these on hand for rare cases when the Rhino adapter can’t screw into the campground’s sewer connection properly. Its so rare though that I’ve never actually used it.
Step-by-Step Dumping Process
- Put on gloves – Don’t skip this
- Connect everything – Make sure all twist-lock connections snap into place
- Set it up downhill – Let gravity do the work. Not always possible depending on campsite layout
- Keep hose straight – Avoid tight turns. When water starts flowing, curves can cause things to move around
- Dump BLACK tank first – Pull the black valve slowly, watching the whole setup to make sure nothing goes wrong
- Use black tank flush if you have one – Let it run until it stops (or runs clear)
- Close black valve
- Dump grey tanks – This washes out the sewer hose. If you have multiple grey tanks, dump the “dirtier” one first (kitchen before bathroom)
- Add water to black tank – Go inside and fill the toilet bowl and flush twice. That’s 3-4 gallons that stays in the black tank to keep seals wet and control odor
- Clear the hose – If you couldn’t get a completely downhill setup, do the “hose dance.” Starting at the camper end, raise the hose and walk it toward the dump station, pushing all water out
- Disconnect and store – The RhinoFLEX has caps for both ends so I don’t rinse it any more than the grey water did.
Water System Tips and Gotchas
- Always leave a bit of water in the toilet bowl – Helps with odor control and keeps the seals wet. If the toilet seals are leaking I sometimes use MolyKote. DO NOT use Vaseline or other petroleum based lubes as it can damage the seal.
- Turn off pump and/or water spigot when away from the camper – Prevents surprises like flooding
- Keep water in P-traps – Just like at home, keep water in sink and shower drains to prevent sewer odors from coming up
- Sanitize the fresh water system annually – We do it once a year in the spring
- Don’t run black tank flush with dump valve closed – You don’t want to accidentally overfill the tank!
- NEVER run the hot water heater dry – Always confirm there’s water in the tank before turning it on
- Tank sensors are unreliable – Don’t panic if they show full when you know they’re not. Trust your experience
Ready to Upgrade?
Now that you understand how your RV’s water system works, you’re ready to start making improvements. Whether you’re planning to add a water filtration system, upgrade to a tankless water heater, or install a pressure monitoring system, having this foundation will make any modification project go much smoother.
There can and are variations on these systems, but this covers the vast majority of RVs on the road today. Always refer to your specific camper’s manual for any unique features or requirements.
Questions about your specific setup? Drop a comment below and I’ll help you figure it out!