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S&S Swan Maintenance - Swan 47 - water tanks overflow “valve “?
01 September 2021 - 05:32
Join Date: 21 February 2019
Posts: 5

Swan 47 - water tanks overflow “valve “?

Dear Fellow swan lovers 

we have 5 water tanks on our swan 47, each with a separate overflow to the sink. I like this design.

On one(1) of the water tanks the overflow pipe has been routed up under the pilot bunk and a "silver fitting " has been fitted.

>> what is the function of this "silver fitting" , see photo<< 

thanks in advance 



Sliver fitting

Overflow at sink

01 September 2021 - 08:38
Join Date: 29 January 2007
Posts: 1018

Dear Chris,

there is exactly the same item on the Swan 38, under port side pilot berth, it should be to breake a possible air bubble, and you can turn the knob to close it (don't do it) hope I am not wrong, in that case Lars will correct me!


Fair winds!

matteo (47/069 Vanessa)

01 September 2021 - 12:58
Join Date: 05 August 2010
Posts: 162

We don't have this fitting so I do not know its precise function. However, I think that an air bubble in the tank overflow tube should not pose a problem, as the overflows guarantee air supply to the tank. In any case, the tubes run above the tank, and an air bubble can only collect in a relative apex or high point. I believe in this case the water creating the bubble would simply run off to its side. End of bubble.
Could it be that the fitting is rather to drain a possible water pocket if the tube is not consistently ascending towards the vents?

As I said, we don't have one, so I don't know ...

best regards,
Martin (Vellamo, 40/039)

01 September 2021 - 18:01
Join Date: 02 January 2008
Posts: 1547

Dear all

Martin is right
The routing of tank vent pipes is rather demanding, as they have to be steadily  descending from their highest point, so the pipes always drain
by themselves. The highest point can be anywhere between the tank and the sink
A low point somewhere along the way creates a water pocket, which prevents the  venting of the tank in the normal way. The pressure water pump will pull the required air through the water pocket, but at an added suction level depending on the water depth in the pocket
If the plumber doing the installation sees that a low point is unavoidable, he installs the shown fitting at the low point. The fitting should normally be kept closed, and opened after taking water, making sure that the water coming out does not cause trouble. When the water in the pocket has drained out, the fitting can be closed again.
It is likely that most owners are not aware of the existence of these fittings
When filling the tank there is no need to to touch the fitting
Kind regards

01 September 2021 - 18:18
Join Date: 29 January 2007
Posts: 1018

Thanks Lars and Martin!!!

your knowledge is helpful and  unique!!!

Fair winds,

matteo (47/069 Vanessa)

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