Level Indicator

Level indicators for plastic tanks: check liquid levels at a glance

Do you need to know how much liquid remains in your tank without opening the lid?

An external level indicator allows you to see the liquid level inside a tank through a transparent tube installed vertically on the tank wall.

The liquid level inside the tube follows the level inside the tank. Operators can therefore check the level visually without opening the tank.

Agrico Plastics offers installation services for level indicators when preparing certain plastic tanks.

Does every tank need a level indicator?

No.

Many natural polyethylene tanks are translucent, allowing the approximate liquid level to be seen through the tank wall. Some models also have molded graduations to help estimate the remaining volume.

A level indicator is particularly useful on opaque black tanks, where the liquid level cannot be seen through the walls. It also provides a quicker, easier visual reading when the tank location, size or operating conditions make viewing the liquid through the wall less practical.

It is important to distinguish a visual level indicator from an electronic measurement system. The indicator presented here uses a red ball that rises or falls inside a transparent PVC tube. Applications requiring automated measurements, alarms, remote monitoring or precise level control may require a probe or another suitable monitoring system.

How does an external level indicator work?

The indicator is installed vertically on the side of the tank.

The assembly includes a transparent PVC tube connected to the tank through fittings and isolation valves. Liquid enters the tube from the bottom, causing the red ball to rise to the level corresponding to the liquid inside the tank.

The Agrico configuration includes:

• A transparent PVC tube
• Two PVC bulkhead fittings
• Two PVC elbows
• Two PVC ball valves
• Gaskets suited to the configuration

The valves allow the level indicator to be isolated from the tank when necessary.

The indicator must be planned according to the tank

Installing a level indicator requires openings in the tank wall for the necessary bulkhead fittings.

The position of these fittings must therefore be determined according to the tank and its intended application.

Adding an indicator after selecting the tank should not be assumed possible without checking the configuration. Tank shape, available space, stored liquid, chemical compatibility of components and other connections must all be considered.

When ordering a new tank, it is preferable to determine from the beginning whether a level indicator is needed. Agrico Plastics can then assess project feasibility and install the necessary fittings before the tank is put into service.

Check compatibility with the stored liquid

The level indicator and its components come into contact with the liquid inside the tank.

Compatibility must therefore be evaluated not only for the tank material but also for the tube, fittings, valves and gaskets.

Each component must be suitable for the stored product and operating conditions.

An indicator intended for one application should not automatically be used with another liquid simply because it can physically be installed on the tank.

A visual level indicator is not a precision volume meter

The primary purpose of the indicator is to show the liquid level.

It should not automatically be considered an instrument that precisely measures how many litres or gallons remain inside the tank.

Tank shape affects the relationship between liquid height and actual volume. The same change in height does not necessarily represent the same volume in different tank designs.

If your process requires precise measurements, level alarms, automated control or remote monitoring, another measurement system should be evaluated.

Special considerations for double-wall tanks

Adding an external level indicator to a double-wall tank requires special attention. The same type of indicator is not necessarily suitable.

Unlike a single-wall tank, where the indicator connects through the side wall, a double-wall tank may require a top-entry measurement solution to avoid penetrating the outer containment wall. Agrico Plastics must evaluate this configuration before any modification.

For double-wall tanks, a dedicated level measurement or control system is often preferable to a conventional external sight gauge.

Plan the indicator when configuring your tank

A level indicator is one component of the overall tank installation.

When preparing a tank, inlets, outlets, drains, vents, bulkhead fittings, valves, Camlock fittings, hoses and equipment connections should also be considered.

Planning these components before installation generally helps avoid modifications once the tank is already in service.

Visit our Tank Applications page to learn about Agrico Plastics' tank-related services, or explore our tank fittings and accessories for other installation components.

Frequently asked questions

Why use a level indicator if the tank wall is translucent?

Level indicators are particularly useful on opaque black tanks, where the liquid level cannot be seen through the wall. They also make visual checks easier when the tank is difficult to access or the liquid is hard to see.

Does the indicator show exactly how many litres remain?

It primarily shows liquid height, not necessarily an accurate volume measurement. Tank shape and dimensions affect the relationship between liquid height and remaining volume.

Can a level indicator be installed on any tank?

Not automatically. Tank configuration, possible fitting locations, the stored liquid and component materials must all be evaluated.

Can Agrico install an indicator on a tank already in service?

Agrico Plastics installs level indicators only on tanks still at its warehouse, before shipment and commissioning. Installation requires openings and fittings in the tank wall.

Why does the indicator have valves?

The valves allow the indicator to be isolated from the tank if the gauge is damaged or maintenance is required on the tube or its components.

Can a visual indicator be installed on a double-wall tank?

A conventional side-mounted sight gauge is not recommended when it requires penetrating the outer containment wall. An alternative level indicator or measurement system must be evaluated with Agrico Plastics.