A high-pressure electrolyser system comprising: an electrolyser stack provided with an oxygen gas outlet and a hydrogen gas outlet and a water inlet for filling the electrolyser stack with water, a water inlet valve configured to provide a one-way valve functionality of the water inlet, and pressure compensating system comprising: a fluid pipe having a first fluid pipe portion and a second fluid pipe portion, wherein the first fluid pipe portion has a first fluid inlet and a first fluid outlet for a first fluid flow (O 2), wherein the second fluid pipe portion has a second fluid inlet and a second fluid outlet for a second fluid flow (H 2) separate from the first fluid flow (O 2), wherein the first fluid inlet is connected to the oxygen gas outlet and the second fluid inlet is connected to the hydrogen gas outlet, and a pressure compensator arranged in the fluid pipe, separating the first fluid pipe portion and the second fluid pipe portion, wherein the pressure compensator is configured to move in the fluid pipe between the first fluid outlet and the second fluid outlet to thereby at least partially obstruct one of the first fluid outlet and the second fluid outlet in response to a pressure differences between the first fluid pipe portion and the second fluid pipe portion to provide pressure compensation between the first fluid pipe portion and the second fluid pipe portion, wherein in a direction from the first fluid inlet to the second fluid inlet along the fluid pipe, the first fluid outlet is arranged after the first fluid inlet followed by the second fluid outlet followed by the second fluid inlet. an electrolyser stack provided with an oxygen gas outlet and a hydrogen gas outlet and a water inlet for filling the electrolyser stack with water, a water inlet valve configured to provide a one-way valve functionality of the water inlet, and pressure compensating system comprising: a fluid pipe having a first fluid pipe portion and a second fluid pipe portion, wherein the first fluid pipe portion has a first fluid inlet and a first fluid outlet for a first fluid flow (O 2), wherein the second fluid pipe portion has a second fluid inlet and a second fluid outlet for a second fluid flow (H 2) separate from the first fluid flow (O 2), wherein the first fluid inlet is connected to the oxygen gas outlet and the second fluid inlet is connected to the hydrogen gas outlet, and a pressure compensator arranged in the fluid pipe, separating the first fluid pipe portion and the second fluid pipe portion, wherein the pressure compensator is configured to move in the fluid pipe between the first fluid outlet and the second fluid outlet to thereby at least partially obstruct one of the first fluid outlet and the second fluid outlet in response to a pressure differences between the first fluid pipe portion and the second fluid pipe portion to provide pressure compensation between the first fluid pipe portion and the second fluid pipe portion, a fluid pipe having a first fluid pipe portion and a second fluid pipe portion, wherein the first fluid pipe portion has a first fluid inlet and a first fluid outlet for a first fluid flow (O 2), wherein the second fluid pipe portion has a second fluid inlet and a second fluid outlet for a second fluid flow (H 2) separate from the first fluid flow (O 2), wherein the first fluid inlet is connected to the oxygen gas outlet and the second fluid inlet is connected to the hydrogen gas outlet, and a pressure compensator arranged in the fluid pipe, separating the first fluid pipe portion and the second fluid pipe portion, wherein the pressure compensator is configured to move in the fluid pipe between the first fluid outlet and the second fluid outlet to thereby at least partially obstruct one of the first fluid outlet and the second fluid outlet in response to a pressure differences between the first fluid pipe portion and the second fluid pipe portion to provide pressure compensation between the first fluid pipe portion and the second fluid pipe portion, wherein in a direction from the first fluid inlet to the second fluid inlet along the fluid pipe, the first fluid outlet is arranged after the first fluid inlet followed by the second fluid outlet followed by the second fluid inlet.