The stuff that Aster supplies is just Bathtub Caulk... the words on the box are in Japanese, but if you look at the pictures you can see exactly what it was made for.
BUT... if you are wanting to seal the valve chests. Use "steam oil", instead. Just spread it on the gasket material and all over the metal to be joined and put the parts together. No muss, no fuss, and only a bit of a oily mess, but much easier than using the caulking compound. And the next time you have to take it apart it is much easier to do so... plus the gasket material is often reusable.
If you have already used the bathtub caulk on the gaskets then you will need to get new gaskets. But not to fear, no need to order some from Aster. You probably have some mighty fine material to cut new gaskets from in your wallet. One dollar bills (yes, U.S. Currency!) makes good gasket material. (If you really feel like you would like to spend more for your gaskets, you can use a Five dollar bill /DesktopModules/NTForums/themes/mls/emoticons/wow.gif, or if you really, really have expensive tastes, use a $10 /DesktopModules/NTForums/themes/mls/emoticons/blink.gif, $20 /DesktopModules/NTForums/themes/mls/emoticons/plain.gif, $50 /DesktopModules/NTForums/themes/mls/emoticons/pinch.gif, or even a $100 /DesktopModules/NTForums/themes/mls/emoticons/sick.gif, but the cheaper $1 bills are actually just as good.) Use a very sharp, new Xacto knife to cut them out (and if you are carefull you can take the mutilated bill to the bank and get a new one in exchange and not have actually spent any cash for the gaskets! /DesktopModules/NTForums/themes/mls/emoticons/hehe.gif )
Use the bathtub caulk on all the other fittings where a gasket is not used (pipe fittings and such). Using steam oil on the gaskets will seal quite well, and you do not run the risk of getting the caulking onto things it must be kept away from. If you use too much steam oil, that is okay, it is supposed to be in the valve chest anyway!