Means for maintaining desired liquid level between inter-connected tanks

An arrangement for maintaining a desired liquid level between interconnected tanks comprises first and second interconnected tanks 2,3, which are connected by a lower tank connecting pipe 4, and an upper tank connection pipe 5, with an inter-pipe connecting pipe 6 therebetween. Preferably, the arrangement is used in a redox flow battery, with the first tank 2 containing positive electrolyte 2b, and the second tank containing negative electrolyte 3b. Both tanks preferably have a void 2a and 3a respectively, for air or other noble gases. The peak 4a of the lower tank connection pipe may be curved upwards, and is designed to remain below the normal liquid level 7 of both tanks, in contrast to the upper tank connection pipe 5 which remains above the desired liquid level. The arrangement is useful if one tank 3 is punctured to cause a leak 8, since this would prevent excessive syphoning of liquid from the other tank 2 to the ruptured tank, and it also prevents the occurrence of airlocks, which may be formed when the tanks are linked by a single pipe only.