A tunnel-type dishwasher comprising a water supply line for receiving clean water to be used in the dishwasher ; a wash item entrance for receiving a feed of wash items to be washed by the dishwasher ; a wash item exit for discharging said wash items when they have been washed by the dishwasher ; a rinsing section upstream, with respect to a feed direction of said wash items, of the wash item exit ; a main washing section upstream, with respect to said feed direction , of the rinsing section ; a pre-washing section upstream, with respect to said feed direction , of the main washing section , the pre-washing section comprising a pre-washing sprayer for spraying a pre-washing liquid onto the wash items, a pre-washing liquid tank for pre-washing liquid that is to be sprayed from the pre-washing sprayer , and a pre-washing liquid inlet configured to receive liquid that has been used in the main washing and/or rinsing section(s) ; and $ a gas discharge flow heat exchanger ; characterised in that the tunnel-type dishwasher comprises further a pre-washing liquid cooler for cooling the pre-washing liquid of the pre-washing liquid tank , wherein the pre-washing liquid cooler is configured as a pre-washing liquid heat exchanger arranged for exchanging heat between the clean water in the water supply line and the pre-washing liquid of the pre-washing liquid tank ; and wherein the agas discharge flow heat exchanger is connected to the water supply line upstream, with regard to a flow direction of the water in the water supply line , of the pre-washing liquid heat exchanger , and configured to exchange heat between the supply water and a discharge flow of air and steam from the dishwasher . a water supply line for receiving clean water to be used in the dishwasher ; a wash item entrance for receiving a feed of wash items to be washed by the dishwasher ; a wash item exit for discharging said wash items when they have been washed by the dishwasher ; a rinsing section upstream, with respect to a feed direction of said wash items, of the wash item exit ; a main washing section upstream, with respect to said feed direction , of the rinsing section ; a pre-washing section upstream, with respect to said feed direction , of the main washing section , the pre-washing section comprising a pre-washing sprayer for spraying a pre-washing liquid onto the wash items, a pre-washing liquid tank for pre-washing liquid that is to be sprayed from the pre-washing sprayer , and a pre-washing liquid inlet configured to receive liquid that has been used in the main washing and/or rinsing section(s) ; and $ a gas discharge flow heat exchanger ; characterised in that the tunnel-type dishwasher comprises further a pre-washing liquid cooler for cooling the pre-washing liquid of the pre-washing liquid tank , wherein the pre-washing liquid cooler is configured as a pre-washing liquid heat exchanger arranged for exchanging heat between the clean water in the water supply line and the pre-washing liquid of the pre-washing liquid tank ; and wherein the agas discharge flow heat exchanger is connected to the water supply line upstream, with regard to a flow direction of the water in the water supply line , of the pre-washing liquid heat exchanger , and configured to exchange heat between the supply water and a discharge flow of air and steam from the dishwasher . <EOS>