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Fresh Water Systems – How They Work & Tips For Maintenance

The freshwater system in most RVs actually consists of two systems; the freshwater tank with an on-board water pump and the city water pressurized fitting.  In either case, pressurized water is supplied to the kitchen and bathroom sinks, toilet, shower, the ice maker is so equipped and exterior shower.

Freshwater tank and on-board water pump.

The freshwater tanks store water on board the RV and supply pressure from the on-demand water pump as a faucet is opened or a toilet flushed.  These tanks vary in size depending on the type of RV and the space available.  Travel trailers and 5th wheels typically have the tanks stored under dinette seats or even the bed platform while basement model units have them stored underneath the floor.

Fresh water tank and on-board water pump.

On most travel trailers, the freshwater tank can be filled with a hose using the gravity feed port.  Make sure you use an FDA approved drinking water hose to fill and store it in a clean sanitary space. Simply insert the hose and begin filling.  The freshwater tank will have a vent hose either at the top or in the fill line.

Some basement models have a valve that will allow you to fill the freshwater tanks while connected to city water.  Connect your drinking hose to a faucet, then your city fill connection, turn the valve and the fresh water tank will fill.

The on-demand pump is typically located next to the freshwater tank and runs on 12-volt power provided by the house batteries.  A switch turns the pump on and off and is typically located in the kitchen area, however, more manufacturers are putting another switch in the bathroom and some a third outside at the exterior shower.  When the switch is on, the pump senses the need for pressure and cycles on and off as needed.  Some of the smaller pumps provide on cost-effective trailers only provide low pressure of 20-30 psi while larger ones will provide 40 psi or more.

City Water

When connected to a pressurized city faucet such as the campground source or an outside faucet at home, pressurized water is provided by the city valve and bypasses the freshwater tanks and pump automatically.  The only thing required by an owner is to make sure the water fill valve is turned to the normal flow or operation on models that have this feature.

Water Pump

The water system in most campgrounds will utilize a well and pump and can provide more pressure than some RV plumbing systems can handle.  My folks went to visit my brother and his family and hooked up the water hose to the outside faucet and then to their city water connection.  Several hours later as they went to their rig for the night they found the entire floor soaked!  Nothing broke, however, the fittings could not handle the 60 psi the exterior faucet provided and needless to say, they had an unforgettable evening.  It is a good idea to have a pressure regulator set at 40 psi on hand as you never know what the pressure will be.  Also, every campground is required to have an annual inspection of their water quality and post an MSDS sheet in the office, however, the water system could pass inspection but have high levels of rust, calcium, and other minerals.  I always have a water filter connected to the pressure regulator before the hose coming into my RV just to make sure.  This also filters the hard water to help reduce the faucets from getting clogged with calcium, lime, and rust.

In-line water filter

Another option is the in-line filter from Shurflo and others which is a little more convenient, however, the entire filter needs to be changed rather than just a cartridge.

Water Pump

Water Pump The water pump does not require much maintenance other than winterizing and occasionally cleaning the in-line filter.  The filter is typically connected to the inlet side of the pump as seen in this photo on the top with “Pink” RV antifreeze.  If your water pump “cycles” or runs intermittently without a faucet on, there is a leak somewhere in the system as pressure drops at the pump and it turns on.  If this happens, make sure all faucets are off and check for leaks in the faucets, toilet, ice maker, and exterior shower.


One of the most important issues with the freshwater system is winterizing which means to keep everything from freezing!  When water freezes it expands and that means bursts in water lines, water heater tanks, faucets, the water pump, and other items that can cause a substantial amount of damage and costly repairs.  It is critical that you winterize your freshwater system by either draining all the water or using RV antifreeze.  Check out our archives for both methods.


Having grown up in a rural community and spending a lot of time on my grandparents’ farm bailing hay and walking beans, I love the taste of well water!  However, after it sits in a freshwater tank for too long, it starts to get a little undesirable!  Drain the water tank completely then refill it with fresh water to ½ capacity.  Mix in ¼ cup of bleach for every 15 gallons of water through the gravity feed and add a couple more gallons of water after to flush the bleach into the tank.  Top the tank off with more freshwater and drive the RV around the block a few times to mix the solution.  Then turn on the water pump and open each faucet and toilet individually until the bleach solution comes out.  Let it sit for several hours and then drain the system.  Don’t forget about the exterior shower, ice maker, and water heater!

Water System Sanitizer

The bleach taste will dissipate eventually, however, there are several products on the market that can help clean and sanitize your freshwater tanks such as these from Thetford.

About the author: Dave Solberg: Managing Editor, RV Repair Club

For the last 25 years, Dave has conducted RV maintenance and safety seminars, developed dealer and owner training programs, written RV safety and handyman articles, authored an RV handbook reference guide, and logged over 100,000 miles on the road in an RV.

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