Thanks for posting this Zoeb, we have had similar issues on our self managed share boat and have been trying to get to the bottom of it.
The boat is similar in set up to your picture but with a shurflo pump and a red round ball type accumulator located next to the water tank in the bow.
The pump will run randomly for about 5 - 7 seconds every half hour or so even when there is no demand for water.
I have checked everywhere I can think of and there are no indications of any leaks in the system, I even spent a couple of hours replacing the electronic flush valve in the thetford as one of the group thought there was water leaking into the toilet bowl. This made no difference whatsoever.
Last night I closed the water shut off valve (which is only about a foot after the pump) and after about 25 minutes the pump ran again for a few seconds, this to me indicates the problem is at the pump / accumulator end. The pump is relatively new looking but the accumulator is showing signs of age, do they have a lifespan ?.
While now fairly confident there are no leaks filling up the bottom of the boat with water it is still something I'd like to get to the bottom of, one of the issues is that if anyone is sleeping in the forward cabin then the noise of the pump disturbs them, easily got round though by switching the pump off overnight.
I would be really grateful if anyone can offer any other suggestions or advice,
Thanks.
Sorry for the hijack Zoeb,
Waterdog.