A Water Level Indicator for your Rainwater Tank

  • Home
  • >>
  • Blog
  • >>
  • A Water Level Indicator for your Rainwater Tank

Many gardeners use a water butt or two to collect rainwater for their plants. From the outside, however, the typical water butt or rainwater barrel does not make its current water level status easily apparent. Although it is usually not too much of a hassle to lift the lid and look inside, a better solution would be to have a water level indicator visible on the outside of the container.

So, a number of commercial and home DIYers have created their versions of a rainwater tank level indicator, which are reviewed below. 

The Transparent Tube System

First on the list of designs is what we are calling the transparent tube system. In the commercial space, the Waterbutt Gauge makes use of this design. The Waterbutt Gauge is an after-market accessory that can be fitted to just about any home water butt. It essentially consists of a transparent plastic tube attached to the outside of a water butt that connects via an opening made at the bottom.

The connection to the bottom allows water inside the water butt to flow freely into and out of the transparent tube. As physics dictates, water will always move in and out of the tube to match the water level inside the water butt. By monitoring the level of water inside the transparent tube, one can easily monitor the level of the water inside the water butt itself.

The Water Butt Gauge

The Waterbutt Gauge

There are, however, a couple of drawbacks with this type of system. Firstly, drilling a hole into the bottom of a water butt is never a good thing! The drilled hole introduces a point of weakness into an otherwise watertight system which has the potential to leak. The second issue is that the transparent tube is susceptible to getting dirty from rainwater residue or from algae growing within the light-exposed damp environment of the tube. This can eventually make seeing the water level inside the transparent tube more difficult.

A good amateur version of this type of rain barrel water level indicator made by Youtuber Green Tech Town has addressed some of these issues. His version of the system tackles the problem of algae growth by covering the transparent tube with a length of pipe insulation. To know the water level inside the water butt, the insulation simple needs to be raised to allow for tube inspection. The one (minor) caveat with this, however, is that having to physically remove the insulation goes against the original aim of having a hands-free water level status indicator.

Green Tech Town's Transparent Tube Water Level Indicator
The rain barrel level indicator by Green Tech Town
The rain barrel level indicator by Green Tech Town
The rain barrel level indicator by Green Tech Town

The Counterweight System

A second type of water level indicator that is commonly used on rainwater tanks is what could be called a Counterweight System. This design involves the use of an internal flotation device which rises and falls with the water level inside the rainwater tank or water butt. The float is tethered to a counterweight on the outside via an opening at the top of the water container. As the flotation device moves up and down with the changing water level, the outside counterweight moves in unison (either in a parallel or antiparallel direction). By observing the position of this counterweight, one is then able to infer how full the water reservoir is from the outside.

A couple of different variations of this system exist:

1. Single Counterweight Design

Amateur DIY-built systems and some commercial products follow the most basic of this float-counterweight design. In this simple system, as water inside the water container increases and the float rises, the external counterweight, that is directly attached via a tether, moves downwards. Therefore, the lower the position of the counterweight, the more water there is in the tank.

DIY-built examples of this design include one made by Youtuber Jasons Jungle. His version consists of a bottle opener as the external counterweight / marker connected by rope to a sealed, partially water-filled plastic bottle inside the water butt.

Jasons Jungle water butt level indicator showing the external counterweight marker

Jasons Jungle water butt level external counterweight / marker

The entry point for the tether used in Jasons Jungle water butt level

The entry point for the water butt level tether

Some DIYers have taken this counterweight design one step further by including some form of guide line for the external counterweight. In the case of Youtuber Willie Koorts, his device adds a length of stiff metal rod to the outside of the water tank on which the counterweight (in this case, a nut tethered via a fishing line) rides. This is useful to ensure that the counterweight does not move too much from side to side especially on windy days.

Willie Koorts water butt level indicator showing the external counterweight marker

The counterweight (nut) on Willie Koorts' water level marker travels along a wire guide

Willie Koorts water level indicator showing the bottom of the counterweight guide

The bottom of the wire guide

Other guide mechanisms for the external counterweight can also be used. One such method is the use of a transparent tube to contain the counterweight completely. This is used by some systems from the Swedish company, Nikeson (see images below).

Nikeson Simple Counterweight System
Nikeson Simple Counterweight System

In addition, commercial systems (and some avid DIYers) typically make use of pulley wheels to smooth the movement of the tether connecting the float to the counterweight. 

Pulley wheels smooth the movement of the tether in Nikeson's Simple Counterweight System

Pulley wheels on Nikeson's LiquiLevel CR

2. Double Counterweight Design

For larger water tanks, an additional intermediate weight is often added inside the water container. This extra component allows the outside counterweight to rise and fall in parallel with the internal float rather than moving antiparallel to it. In this way, the height of the external indicator shows the actual level of the water inside the reservoir.

C-Level Rainwater Tank Level Gauge from Freeflush Water Management

C-Level Rainwater Tank Level Gauge from Freeflush Water Management

Liquilevel ST from Nikeson

Liquilevel ST from Nikeson

Some amateur enthusiasts have also built their own version of this double counterweight system such as Youtuber Homesteadonomics (see video below).

Ultimately, however, the double counterweight design is more the realm of larger water tanks than it is of smaller water butts found in most people's gardens. However, this design may provide some DIY enthusiasts with an idea of how to take their counterweight-based water butt level indicator to the next level!

The Flag System

Tanks Direct's VisiBall Water Level Indicator

Tanks Direct's VisiBall Water Level Indicator

Another design sometimes used to monitor the water level inside a garden water reservoir is what we have named here as the 'Flag system'. Similar to the Counterweight system, this consists of an internal float connected to an external marker. However, instead of using a flexible tether to link the two, a rigid pole running through a guide tube at the top of the water tank forms the connection. At the top of the pole, some kind of high-visibility marker is attached for ease of observation.

As the water level in the reservoir rises, so too does the float which in turn pushes the pole out of the guide tube at the top of the tank. Therefore, the further the high-visibility marker, at the top end of the pole, is raised above the tank, the higher the water level within it.

This is best illustrated by Tanks Direct's VisiBall Water Level Indicator (see image above). This commercial system is primarily designed for larger water tanks but a small DIY version of it for a smaller water butt should not be too hard to put together.


The need for a water level indicator on rainwater tanks and water butts has prompted the development of various designs by both commercial companies and DIY enthusiasts. Whether it is the transparent tube system, the counterweight system, or the flag system, these water level indicators all enhance the convenience and efficiency of rainwater harvesting systems for gardeners of all levels.

Related Posts

Which Plastics Are Safe for Growing Vegetables and Food Crop Gardening?