Because there is minimal configuration overhead (from an Office Web Apps perspective) and zero data loss, there is little risk to rebuilding a farm. These steps can be a legitimate part of an action plan for resolving technical issues with Office Web Apps.
1. Take farm offline (if there is a load balancer)
2. Collect the current Farm information via Powershell (on WAC Server):
Get-OfficeWebAppsFarm > c:\MyWACfarm.txt
3. (If multi-server farm) use Powershell (on WAC Servers) to remove each child machine from the farm, then remove the parent machine. This will delete the farm.
4. Reboot the Office Web Apps server(s).
5. Recreate the farm via Powershell (on WAC Server) using (if appropriate) the parameter values from "MyWACfarm.txt".
New-OfficeWebAppsFarm -InternalURL "http://WACServer.corp.contoso.com" -AllowHttp -EditingEnabled -OpenFromURLEnabled
6. Reunite the children with their parent via Powershell (on WAC Server). Run this from each child server:
New-OfficeWebAppsMachine -MachineToJoin <ParentServer>
7. Bring farm back online.
Note: You may want to rebuild the bindings via SharePoint Powershell (on SharePoint Server):
New-SPWOPIBinding –ServerName “WACServer.corp.contoso.com” -AllowHttp
Note: Anything above in Red you need to replace with the correct information from your farm.
Configure Office Web Apps for SharePoint 2013