There are some really simply tests to check whether your valves are leaking or not and all you need is a soapy solution and a brush.
Inflate your tubes / inflatable as normal.
To check whether the valve is adequately sealed into the inflatable, or whether air is escaping from between the valve and material, brush soapy solution around the outside of the valve. If bubbles form, the valve is leaking and probably just needs a gentle nip, to tighten it up. Once tightened with the correct valve tool, retest the valve. If it still leaks, it’s worth removing the valve to clean all the valve and fabric surfaces, before reassembling the valve and retesting it again.
Check whether the valve leaks from the cap, by brushing the soapy solution around the entire cap. If bubbles form, the cap or cap seal should be replaced. It’s worth noting that some caps are more of a dust cover, whether others are very much secondary seals.
And the final test, is checking the valve mechanics. With the valve cap removed to expose the mechanics, brush the soapy solution across the valve to form a single bubble. Wait a short while and watch the formed bubble to see whether it grows. If the bubble grows, the valve is leaking and either a service kit or valve replacement is required.