Hi all.

Excuse my ignorance here but hopefully no such thing as a stupid question.

I thought you would have an answer from a 470 owner by this time. 

We do not have a 470 but some quick research found that most 470 have two heads and two small sullage tanks of about 30ltrs each. In the heads there will be a valve to open to release the sullage from the tank. The tanks will be fitted above the water line to enable them to empty by gravity. The fact you have two "sullage" deck fittings points to your boat having two sullage tanks. The tanks would be fitted in the heads area behind the fitout. The valve is likely to be adjacent to the toilet behind the fitout accessed by some sort of small door or hatch. 

Regarding the water tank question the only thing I could find was the tankage total was between 380 and 400 litres. If you only have one filler but two tanks they must be linked. I would expect there is either an isolation vale or selector valve in the fresh water system somewhere you just need  to look.  

Enjoy your new boat.

Not sure about the water tankage. Our boat has one tank under the bed in the forward cabin filled at one cap on the starboard bow labeled “water.” The tank is accessed by a lift-off panel under the mattress. There should be a small key with two prongs that fits all of the caps.

Hope that helps some.

It’s also true you have 2 small black water tanks, one per each toilet. That’s why you have 2 waste caps on the deck, port side. In my boat you can’t easily take the locker panels to see these black water tanks as these panels are bolted, but both has a vertical ‘window’ to control the tank level (a shame that Hanse didn’t install a level gauge from factory here, actually is my first sailing boat without a gauge on the black water tank). As someone said, if you never filled them up it’s because the ball valves are open and everything you do on the toilettes is going directly to the sea water (the aft cabin valve is under the floor board just at the entrance of the toilet, the front head one is under the sink, accessible by the locker).

Still regarding the water tanks, both fill up at the same time but you can control which one you use. There are 2 red ball valves under the floor board on the right of the saloon table, each one closes one water tank.

This may be slightly different from boat to boat, even on the same model. Mine is 2010 470e.

There are four water tanks on a 470, although two are inside one on each side, baffles!

It is possible to fill all tanks from one filler but you'll have to wait for gravity to balance the levels out, so best remove both tops to allow air in and fill to the overflow kicks in on one then fill the the other.

As most of the weight has been badly located to a port bias, batteries and navigations hard ware. I tend to close the starboard tanks so that water used is from the port side only, evening out the weight distribution and then judge when to adjust. I have a manifold with four valves.

The day heads and that of the master cabin are also on the port side and if you have the seacocks closed these will fill up.  A suction pump can be inserted into the pipe and remove the waste black water.

You can tell with some experience as to how full they are by simply tapping on the sides nd listening to the note coming back.

They are interconnected and can be separated by a shut off valve. (Under midships floor board starboard side near table pedestal)

Be careful of the sensors. They break easily. But easily repaired. 

Watch water indicator intake on your instrument panel as each tank fills. The filler cap hose is on starboard side and follows from beneath deck cap next to interior fed bulkhead down to tanks. Takes a good while fill.