Hello! First, thank you very much.
I have a submersible pump that fills the tank in height (I don't have mains water), and from that tank water is supplied to the house by gravity. From the tank comes a pipe with a T where a pipe for hot water and another for cold.
Thank you!
Then the only solution that I see is to pressurize the tank - home section. Put an economical hydropack with a level switch float in the tank that activates / stops the hydropack pump before the water runs out in the tank. With this system the water will end up the same but when the water arrives again the hydropack will pressurize the system again. The non-return valve that you already acquired alone does not work, but if you want to try my recommendation you must go between the tank and the pump. Luck
There are also simpler and cheaper devices to increase the water pressure in the circuit
https://articulo.mercadolibre.cl/MLC-477606667-aumentadora-de-presion-p-calefont-129g-equipos-y-bombas-_JM?matt_tool=92529271&matt_word&gclid=Cj0KCQjwn8_mBRCLARIsAKxi0GJC_VDH0nVg2sO98A_DY1ly7bTK7WVx4Z4HXzQJ2Avnk-SLWrjlM6caApEcEALw_wcB&quantity=1
But it is necessary to understand that with the system that is currently installed there will always be the possibility that the tank will run out of water.