Size of water tanks on 777

[kenpimentel]

I'm writing a book and the 777 plays a big role in it. I'd like to know how big are the individual potable water tanks are on a 777. I know the total capacity of potable water on the plane, but I don't know the size of each one. I believe they are made of carbon fiber? That would be useful to know too.

thanks in advance

[LME (GOD)]

For 777-200/300....(the standpipe is a company mod)

Purpose
There are three water tanks to hold potable water.

Physical Description
Each water tank has a capacity of 120 gallons (454 liters). There is a standpipe that limits the amount of water in each tank to 109 gallons (413 liters).

[kenpimentel]

Thanks a bunch!