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This Easy Mod Will Fill Your RV Water Tank Faster

RV water tank

This Easy Mod Will Fill Your RV Water Tank Faster

My previous article addressed a slow filling fresh water tank when using the gravity fill and how to improve the filling procedure. If last week’s suggestions didn’t resolve your slow filling RV water tank, take the advice of David at David’s RV tips blog, who recommends,

Turn the water faucet down a bit and let the tank fill at its own slow pace.

Or, consider employing one of the two following modifications that will allow you to quickly fill your RV water tank under pressure via a city water faucet.  Note: Some RVs are already set up with this feature.

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Slow filling RV water tank

As I shared last week, my slow filling fresh water tank took forever to fill, wasting my time and annoying those in line behind me at public filling locations. Even when using a fill hose as suggested in my last post, it was time-consuming.

To remedy this problem, I decided to rig up a pressure fill system that would fill the tank via city water flowing directly into the water tank, venting the displaced air out the existing vent and the 1.25” gravity fill line.

How to fill your RV water tank using pressure

The first and most common way to perform this modification is to install a jumper hose with a shut-off valve between the pressure (outlet) side of the water pump and the pickup (inlet) side of the water pump.

Since the water pump acts as a check valve preventing city water (when you are hooked up) from flowing backward through the pump into the fresh water tank, jumping a hose/pipe between the inlet and outlet will allow pressurized city water to freely flow from the outlet side of the pump to the inlet side of the pump and into the tank, eventually filling it to overflowing.

Some RVers have experienced this inadvertently when their water pump failed to act as a check valve as this video demonstrates:

With the completion of this modification, filling your RV water tank when hooked to city water is simply a matter of opening the valve, resolving your slow filling water tank problem once and for all.

In my situation, there was no room allowing me to break into the pickup line between the pump and where the line enters the RV through the floor from the fresh water tank below deck. With no room to install a tee in the line and limited access to work on either side of the pump, I had to come up with an alternative.

RV water tank
The most common method

Our DIY pressure fill system

The easiest solution for me was to replace the readily accessible drain plug on my fresh water tank with a ¾” threaded garden hose fitting and shut-off valve. I then attached a short length of garden hose to the fitting coming out of the tank and secured it just below the sidewall edge of my RV. This left me with an easy-to-access female garden hose fitting.

Finally, I added a plug into the end of the hose to keep dirt out of the fitting. This modification allows me to quickly fill my fresh water tank via a city water hookup under pressure and full volume while utilizing my 1.25” gravity fill line and existing tank vent for air to escape the water tank as fast as fresh water can enter.

The author’s modification

The filling process now takes only about 5 minutes, eliminating the slow filling tank issue. The following are the step-by-step instructions to help you visualize my filling process:

  • Remove the male garden hose plug used to keep road dirt out of the pressure fill inlet.
  • Attach the male end of an approved potable water hose (female end hooked to a city water faucet).
  • Remove the cap from the gravity fill so air and excess water can easily escape from the water tank.
  • Open the shut-off valve at the bottom of the water tank.
  • Turn on the faucet, allowing pressurized water to flow through the potable water hose into the bottom of the fresh water tank.
  • Fill water tank to desired level by either watching the monitor panel or watching for water to begin to flow out of the gravity fill indicating a FULL tank.
  • Reverse the process when done.
The pressure water fill hookup on the author’s RV


With either of the above two modifications, be absolutely certain that air is escaping the fresh water tank as quickly as water is entering. If water is entering faster than air is escaping, the water tank will expand with water like a balloon and we all know what happens when a balloon bursts!

When I need to drain my fresh water tank, I just disconnect the short length of the hose and open the valve which allows water to spill onto the ground.

Use one of the two modifications described above to solve your slow filling RV water tank issue and enjoy more time camping. Read more about our slow filling water tank here.