I believe you are talking about accumulator tanks which reduce pressure cycles and smooth water flow. The tank itself may be an issue...make sure the pressure valve is closed. If there is constant cycling...there is either a small air leak in the system or a faulty pressure valve on the pump. The latter is the place to start as it is easier to diagnose and fix or eliminate as an issue.
If there is a leak...the place it will likely be is at a joint/hose clamp. Tighten all of those and look for obvious issues like water drips as a first step. If that does not do the trick the only alternative is to eliminate the section of hose where the loss is occurring by working forward from the pump outlet to the individual joints and removing the hose at those joints and plugging the hose up tight. If the pressure holds...then move on to the next joint etc. until you find what section is at issue and then simply inspect and/or replace it.
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