I recently had a flooding in my apartment due to a broken hose under the kitchen sink. Now I'm worried about everything that could go wrong again in that sense.

Then I noticed this device that sits between the tap in the bathroom and the hose that connects to the washing machine. I thought this was something to prevent water leakage in case the hose would be damaged. But then I disconnected the hose from the machine and let the water run freely to see if it would automatically stop at some point, but it didn't. I couldn't notice any limitation on the water flow.

Tried to look for that online but couldn't find anything. The only similar device to this was one that allows water to go only in one direction, but that device usually had a switch and this one doesn't have anything. There is a device just like this one attached to the water supply for my dishwasher.

Can anyone tell me what is this thing and what it does?

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  • Because such things may have "regional looks" or be more common in some region or country; where, roughly, in the world, are you, and the device? To me, it looks like it's probably a "swing check" valve, (to allow water in only one direction) and I don't associate those with "having a switch" as you describe finding them.
    – Ecnerwal
    Commented Aug 10, 2021 at 15:29
  • @Ecnerwal OP is based in Austria based on their profile. Electrical plug is consistent with a European setting.
    – GOATNine
    Commented Aug 10, 2021 at 15:30
  • 1
    Looks like it have been made for the washing machine. Would contact maker of washer or look in the washer manual(google might find manual also). Might be a filter housing.
    – crip659
    Commented Aug 10, 2021 at 15:34
  • Judging by what looks to me like an adjustment screw on the top, I'm going to guess that it's a pressure regulator/reducer.
    – brhans
    Commented Aug 10, 2021 at 18:01
  • @Ecnerwal I'm based in Austria indeed, as GOATNine figured. Commented Aug 11, 2021 at 15:17

1 Answer 1


It appears to be an "aquastop valve" that shuts off the water supply in the event of a leak. Many brands appear to do this. Here's one example.

The Aqua-Stop design incorporates a dual layer inner hose encased within a hard plastic outer hose. If either of the inner hoses should leak, a specially designed shut-off mechanism will be triggered, blocking the hose and preventing water flow. Help prevent flooding your home; potentially, even a small leak from your washing machine hose can lead to costly and inconvenient property damage. From espares.

I don't know how it works, but WhitegoodsHelp has some more info. The dot on top of yours looks like a trip indicator. Also it only detects a leak in the inner pipe itself and won't react to your disconnecting the other end to test it (which is a good thing since apparently you would then need to replace it as there's no reset button).

If the inner hose ever leaks, then a device inside this housing is able to detect the incident and prevent further water getting into it. If this happens, the hose will no longer let any water through to the appliance and will commonly indicate it has “tripped” via a red dot in a small window in the housing. [...] The hose protects only against the fill hose bursting or corroding [...]

  • It looks like it is the device described in this answer and I wish I could +2 it for pointing out that you cannot test it. If it's wrong, it could be a debris filter, a backflow preventer, a pressure regulator.
    – jay613
    Commented Aug 10, 2021 at 18:47
  • This seems to be it! Found a guy (youtube.com/watch?v=8P4uC1jat_U) exploring a hose just like the one I have for my dishwasher, I'm assuming it's the same I posted the pictures for Commented Aug 14, 2021 at 6:57

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