Vetus waste deck fitting - Help

[Desmo]

Hi
My first time to attempt to empty my waste tank and I find I cant open/unscrew the deck fitting. It is a Vetus item that has a small pull up handle with "WASTE" embossed on it. This handle has a hole through it which I have gingerly tried to lever with a screwdriver as I presume it should unscrew. It has resisted so far and before I apply greater pressure to what looks like an easily breakable handle I thought I should check I am not trying to open it incorrectly.
I cant find any key onboard and although I can see this model still for sale, it isnt matched by either suitable key or instructions to open.
Any insights would be appreciated.

I am currently soaking area with WD40.

 

[SaltIre]

Is this it? Website says it is available with a winch handle socket so presumably it unscrews.
Make boating enjoyable - VETUS

 

[Desmo]

Is this it? Website says it is available with a winch handle socket so presumably it unscrews.
Make boating enjoyable - VETUS
View attachment 138513

Yes thats the one. I cant see how a winch handle would get enough grip in the small recess, but Ill try it. Thankyou.

 

[SaltIre]

I didn't mean yours can be opened with a winch handle. Here's the version with the socket:

Vetus Waste Water Deck Plate for 38mm ID Hose
Maybe complain to them that they haven't made your boating enjoyable...

 

[Desmo]

I didn't mean yours can be opened with a winch handle. Here's the version with the socket:

Vetus Waste Water Deck Plate for 38mm ID Hose
Maybe complain to them that they haven't made your boating enjoyable...

Yes I got that after reading your post properly .
After applying mole grips and a lot of pressure it finally shifted. My version is the chrome option not stainless and had clearly corroded around the threaded area which does not seem to be chrome plated. Greasing and regular use will probably avoid seizing again but the Stainless option would probably be better. It does seem odd that a key is not provided or available and you are left to use whatever leverage you have to hand.

 

[SaltIre]

There is one available with a slot:
Stainless steel deck plate for waste water extraction "WC" for hose D 38 mm, cover D 87 mm, L= 120 mm.
and key:
Key for stainless steel deck entries with slotted cover
but at that price it should be gold plated!

 

[Desmo]

There is one available with a slot:
Stainless steel deck plate for waste water extraction "WC" for hose D 38 mm, cover D 87 mm, L= 120 mm.
and key:
Key for stainless steel deck entries with slotted cover
but at that price it should be gold plated!

Thats for the slotted version not the pull up handle one.