Do large aircraft accumulate water in their tanks? Do large aircraft accumulate water in their tanks? 

If so, how is it drained? How often is it drained? At what rate per hour does it accumulate? If not what was done to circumvent the problem?
AFAIK all aircrafts accumulate water in their tanks. Since you ask for large aircraft acccording to wikipeadia:

FAA definition of large aircraft


  The US Federal Aviation Administration defines a large aircraft as any
  aircraft with a certificated maximum takeoff weight of more than
  12,500 lb (5,700 kg)


EASA definition of large aircraft 


  The European Aviation Safety Agency (EASA) defines a large aircraft as
  either "an aeroplane with a maximum take-off mass of more than 5,700
  kilograms (12,600 pounds) or a multi-engined helicopter."


Here is Airbus A340 draining process with explanations on youtube 
                
            

Here you can find EASA regulations about draining https://www.easa.europa.eu/download/etso/ETSO-C76b_CS-ETSO_11.pdf

Here is FAA regulations about water draining
https://www.faa.gov/documentLibrary/media/Advisory_Circular/AC20-125.pdf

On FAA AC 20-125 p.7 states


  WATER REMOVAL/PREVENTION. Water is best removed from jet fuel by
  passing the through approved filtration/separation equipment. A
  two-hour settling period and the use of floating suction to drain fuel
  from the top of a storage tank are also recommended to help prevent
  water from being introduced into a fuel system. Water will readily
  settle-out of aviation gasoline; therefore, filters/separators are not
  required for water removal, however, they are necessary for removal of
  solids. The best means to minimize the amount of water entering a fuel
  system is the inspection and proper maintenance of equipment and the
  training of ground and flight personnel.


Also FAA AC 20-125, Water In Aviation Fuels, para 7 c suggests that it may be necessary to gently rock the wings of some aircraft while draining the sump in order to completely drain all the water.