I found this in the APOLLO EXPERIENCE REPORT COMMAND MODULE UPRIGHTING SYSTEM on page 23:
I tried to find other reports of that Apollo 7 leak, but I could find none.
Does anybody know another source?
400 pounds of water, that are 180 kg. The pressurized CM cabin volume was 10.4 $m^3$, the CM mass was about 5560 kg. So the capsule was far from sinking.