Dry riser systems are normally dry without permanent water connection to it and depend on the fire truck to pump water into the system. Dry riser system comprises of one or multiple vertical riser pipes or horizontal runs piping that are terminated to the two way breeching inlets located at ground level and connected to the 65mm dia. landing (Fire Department) valve outlets coupled or uncoupled with 65mm dia. 30m long re-inforced rubber lined (RRL) hose. So you cannot use a dry riser for a an automatic sprinkler system. However you can use a dry riser and a sprinkler system in the same building provided you have a separate wet riser for the automatic sprinkler system. - Hope this clarifies the confusion.