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Filling Loops

Filling Loops

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What are Filling Loops?

A filling loop is a component in a sealed heating system, such as a combi boiler. It is used to regulate the pressure in the boiler. The loop may be outside the boiler, or incorporated inside into the design of the system itself. By adjusting the screws on the loop, it is possible to alter the pressure in a combi-boiler and make it more efficient.

Most sealed heating systems need their pressure regulated periodically. The pressure gauge, usually located on the front of the boiler, will give you an indication of the current pressure levels (which should swing between 1.0 to 1.5 bar). Small leaks in boiler components, such as the radiator valve spindles, or automatic air vents, may reduce the pressure and reduce the efficiency, efficacy and lifespan of the system.

The pressure in a combi boiler is regulated via the filling loops. The loop is usually a metallic, silver colored braid located under the boiler or in some models, inside the system. There are two pressure valves at each end of the loop. These valves can be adjusted to regulate the pressure in the combi boiler.

It is recommended that you check the pressure gauge at least once every year and adjust the combi filling loop accordingly.

Types of Filling Loops

Straight Combi Filling Loop

As the name suggests, a straight loop is a long, braided metallic tube with two straight connecting hoses at each end. There is usually a valve at one controlling end which can be adjusted to regulate pressure in the combi boiler. Most loops will have a 'double check valve' to ensure extra safety.

Tee Filling Loops

Like the straight loop, tee filling loops too are made up of long, braided metallic tubes, with one difference: one end of the loop features a horizontal T-joint hose. This end can be connected to two points in certain boiler designs, and features a double-check valve.