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S&S Swan Maintenance - Holding Tank
03 February 2019 - 12:57
Join Date: 27 January 2011
Posts: 111

Holding Tank

Last summer I finally installed a holding tank on IF. The location originally foreseen for that on a 411 is forward starboard just next to the head. The only alternative I considered was to install it in the locker in the head, gravity-based, but in the end I went with Nautor's view, since installation and inspection/maintenance are easier there and it is possible to install a bigger tank. 

I did not find any off-the-shelf tank that would be a good fit, and had a company in Hamburg specialising in holding tanks build one from 10mm PE to my specification. This cost 900 EUR, including sensor, display and fittings. On top of that came a waste pump, Y valve, tubes, wiring, and switches. Installation was an entire day, plus another day for corrections later.

As you see from the photo, the 90l tank takes most of the available space. This was the place where I kept tool boxes and engine liquids. Initially I was at a loss of where to put all that, but funny enough it turned out that by removing superfluous equipment throughout the boat and starting to use the area under the starboard sofa in the saloon we ended up having way more space for food and personal belongings than we had before.

I have not yet installed a tube to the deck for emptying the tank in port. I rarely see pumps in the harbours we go to in the Med. The plan is to install it at some point later, using a second Y valve directly on top of the tank.

In the photo below you see the waste pump installed next to the basin in the head. Pump and toilet exit go to an Y connector shortly above the sea cock. I (so far) did not manage to route the tubes in a way that allows to screw the Y valve onto a wall, so it is free-floating at the moment. In return I managed to retain most of the space below the basin.

A second sea cock for the waste pump exit would have been better, but the approach with the Y connector works just fine.

The tank fittings are well above the waterline.

In the meantime I have changed the ventilation, the filter now being higher up to avoid problems when heeling. The exit of the filter connects to the ventilation of the shower sump in the head, which is convenient. I may eventually move the filter into the upper left locker in the head.

The five of us went onto a 2-month cruise from Marseille to Scarlino via Sardinia last summer with this setup. As expected this turned out to be a significant improvement of live on board.


Christian 411/028 IF


05 February 2019 - 20:54
Join Date: 19 July 2007
Posts: 52

GHi Christian.

Thanks for your interesting post.

We have been looking into installing a holding tank into our 411 Hierro,  and like you have not found a standard tank that will fit into the boat and provide sufficiet volume.

Can I ask the following.

Do you have the original "Baby Blake" WC. Does all the waste pass into the holding tank, to be pumped out or can it be pumped directly from the WC, to the sea via the Y valve? Does the tank extend to the bottom of the locker, I note it is bolted to the inner bulkhead at the top, is it supported from the bottom. Do you have the dimensions of the tank that you could share?

Thanks Again.


Hierro 411 042

06 February 2019 - 18:45
Join Date: 27 January 2011
Posts: 111

Hi Paul,

we have a standard Jabsco head with manual operation. With the Y valve we control if waste goes to the tank or to the sea. When selecting the sea, it goes from the Y valve to the Y connector you see on the photo. There is the risk that it goes up to the pump, via the other branch of the Y connector, but we have not observed that. This would probably only happen if the sea cock is closed. The pump is above the waterline.

The tank sits on the original board in that space and is screwed to the wall in two places as you see on the photo. This way it is squeezed in and not moving in any direction. 

I sent you a message, happy to share the plan!

Christian 411/028 IF


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