Hi @Andyyy,
Thank you for your question.
It does sound like the issue is with the inlet valve, especially if moving the float (what you referred to as the "dipstick") stops the water flow. If the inlet valve is shutting the water off when lifted, it sounds like it's still functioning, and you need to adjust the level of the float on it to shut the water off sooner.
Start by adjusting this and see how you go. If this fixes the issue, there is no reason to replace anything. If it doesn't start by replacing the seal.
Replacing the seal in the inlet valve is a great first step. The Fluidmaster Toilet Inlet Valve Replacement Seal you've linked is a good option, but it's only compatible with Fluidmaster valves. Since you mentioned this is an older Caroma toilet, it's worth checking if the existing inlet valve is Fluidmaster or another brand.
To check, look at the top of the valve or float mechanism for branding, if it's Fluidmaster, the seal you linked should work, if it's not Fluidmaster, you might need an inlet valve seal designed for Caroma inlet valves, such as this FIX-A-LOO Inlet Valve Headseal Washer.
It is also worth taking the old seal in-store with you for comparison purposes.
If replacing the seal doesn't resolve the issue, the entire inlet valve might need replacing. This Caroma Quietflow 2 Bottom Inlet Valve is likely an option, but we'd need to confirm compatibility with your specific cistern.
Let me know if you have any further questions.
Jacob
