Some will interchange. The spacing on the bolts that hold it to the base vary some in width. There is one brand that uses 3 bolts and only fits that one type.
No the standard toilet seat covers are for the standard round toilet seats. The universal will fit the long oblong shaped toilet seats.
To insulate the tank from condensation
Because the sizes have to be the same and be compatible with each other.
Just test it with universal litmus paper or universal indicator(liquid)
not all toilet bowls and tanks are compatible. If your toilet bowl has no holes for a tank it most likely a bowl that is made for a flush valve, or a high or low boy mounted tank.
Try here: http://www.toilettanklids.com/seats.html
actually it uses 49 percent. suprising eh?
universal toilet seat lid cover is a bit bigger than our seat lid toilets. international people don't use toilets we use they use squatting toiets. like in India, china, japan and africa.
Grey is usually dirty water but not toilet water (shower, sink drain) Black (or Brown) is sewage from the toilet. If you have a motorhome there will be two sewage tanks... "grey" and "black"
Yes. 9 Gallons is the maximum that most flush tanks hold.
You should be able to take the old tank off and mesure the distance of the mounting bolt holes and mesure the diamiter of the water hole then go to home depot and mesure some of the tanks they have. I diagree with the previous answer. By the way, it's spelled: measure. Anyway, if you have a 1.6 gallon toilet tank, you should replace it with the same brand. Different manufacturers tanks will NOT work with just any toilet. If you have the old style toilet e.g. 3.5 to 5.0 gallon tank, you would have to find a junk dealer who would have the exact same type of tank.
That is the 'flapper valve' in the bottom of most toilet tanks. This valve is pulled up when you flush, admitting water into the bowl.