I have to repressurize my Vaillant Aquaplus gas boiler, and I couldn't understand from the manual where exactly the internal filling loop should be fitted.

The water pipes don't have any valves directly on them, but the manual states that this model should be equipped with an internal filling loop.

However, I don't see one and I don't see how I would fit one here:


Vaillant boiler bottom view

Can you please clarify where I should fit the flexible loop? This answer mentions a flexible silver pipe but I don't see it in the original picture.

  • 1
    Hello, and welcome to Home Improvement. Good question; keep 'em coming! Commented May 14, 2019 at 19:19

1 Answer 1


Turns out there is no flexible pipe, I guess I was reading the wrong manual. The system can be refilled by simply turning the screw at the bottom, as shown in the pictures.

The boiler needs to be powered off, and the screw (valve) slowly opened while keeping eye on the pressure gauge. Refill slowly to 1-1.5 bar (everything below 2 bar should be fine).

In hindsight, this seems obvious as the screw is right at the connection between the cold water mains and the central heating return pipe:

Vaillant repressurizing screw (filling loop)

There is no need to remove the bottom grill either:

Vaillant repressurizing screw, with grill still on

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