New to motor homing

[Hime traveller]

Hi all, just purchased a homer C class on a ford chassis 2007, have just attempted to fill water tank, noticed water flowing of an overflow pipe which is connected to a unit in the heater cabinet, this unit has what appears to be a turn off control on top and a press button on the side, both blue in colour, when I turn the top control half a turn and then press the lower button the flow of water stops...can anyone advise me what this unit is for and have I done the right thing, sorry for the long winded question but hopefully someone can help...I have a homer manual but there is nothing similar shown.
Thanks Matt

 

[Figaro]

I think it might be the frost protection valve.
Pull up to close for use. At about 4c it will self click down to drain the boiler to protect it against frost.
Is it a Truma boiler ?
You should have a manual for the boiler, if it's not there find the make and model number and you should be able to download it

 

[Figaro]

Welcome to the forum by the way

 

[grasscutter]

Welcome.
Definitely the frost protection dump valve on the boiler.

 

[MikeD]

Hi and welcome to the forum

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[davidbaldam]

Hi and welcome to FUN.

 

[f6c]

Welcome aboard

 

[The Dudess]