Projects 3 & 4 - Holding Tank & Washdown Pump

Holding Tank

The Hanse 415 was not designed as a Great Lakes boat.  She has a 35 litre (7.7 imperial gallons for those not yet converted) holding tank.  That's okay for a weekend jaunt but certainly not for living aboard for two weeks during our summer vacation or coastal cruising south.


The holding tank was the biggest project that Nadil from NM Marine Services did for us. 

Our system is similar to the picture at right.  The discharge from the head goes to a Y-valve, and after the Y-valve one branch goes to the new holding tank and the other goes to our original 35 litre tank.

We decided to install the holding tank under the port aft berth, since there was space there in close proximity to the head.

First Nadil made up a wooden template of the tank, so that he would be sure that it fit, and to provide the manufacturer with exact dimensions. Once manufactured, he braced the tank fore and aft and laterally and strapped it down to blocks bonded to the hull.


I asked Nadil to install two vents because I have read that it is the anaerobic bugs that smell not the aerobic bugs and we wanted to encourage the aerobic ones!

The best quality sanitation hose money can buy completed the system.

While we were at it we decided to install a tank monitor so that we wouldn't have to guess how full the holding tanks are. We selected a multi-tank system so that we could also monitor the original holding tank.  Of course installing a tank monitor means that it needs to be calibrated.  Because the new holding tank was an irregular shape we first needed to determine its exact volume.  We did this by measuring the volume of a bucket and then using the bucket to fill the tank.  You'd be surprised at how long it takes to fill a 178 litre tank (40 imp. gal.) with a 10 litre pail through a small funnel!  Then we had to pump out and then refill it in increments of 10% and program the tank monitor at each increment. Then we had to pump out again!  Suffice to say the dock staff at Hindson Marina where we keep the boat were very patient as we went through the process.


Washdown Pump

We found a 5.2 gpm JABSCO washdown pump on sale at Fogh Boat Supplies and picked it up for Nadil to install.  We decided to install it amidships so that we could reach both ends of the boat with one length of hose.  That actually worked out well because it was adjacent to the head and the access to the original holding tank and its deck fitting. Nadil did a great job of fitting the pump under the shower seat, t-ing the intake into the head intake and running hoses discretely. 

Both the holding tank and pump work just as planned.