What type of Zodiac? Is it a bonafide Zodiac, or another make of inflatable?

In addition to the responses above, try this too:

1. Fully inflate the boat (no need to do the keel) Make sure it's good and pumped up!

2. Confirm all the caps are secured. NOTE: Air leaking with the caps off is perfectly normal. The cap is what makes the valve air-tight.

3. Now, get some soapy water and start slathering the tubeset. Pay special attention to the caps & valves.

Do you get any bubbles anywhere?