A trapway arrangement for selectively fluidly connecting, in a toilet system, a toilet bowl to a drain line, the trapway arrangement comprising: - a horizontally positioned trapway member fluidly connected in an installed state thereof between the toilet bowl and the drain line, the trapway member defining a main fluid passage therethrough; and - a valve member installed within the main fluid passage of the trapway member, the valve member is capable of being adjusted between an open configuration and a closed configuration, wherein in the open configuration the valve member allows contents in the toilet bowl to flow to the drain line through the main fluid passage of the trapway member, and in the closed configuration the valve member restricts the contents of the toilet bowl from flowing to the drain line through the main fluid passage of the trapway member, wherein the main fluid passage includes a first flow region defined on one side of the valve member and fluidly connected in the installed state thereof to the toilet bowl and a second flow region defined on other side of the valve member and fluidly connected in an installed state thereof to the drain line, wherein the trapway arrangement further includes an auxiliary flow member defining an auxiliary fluid passage, the auxiliary flow member mounted on top of the trapway member, and fluidly connecting the first flow region and the second flow region of the main fluid passage, wherein the auxiliary flow member includes a first side arrangement fluidly connected to the first flow region of the main fluid passage, a second side arrangement fluidly connected to the second flow region of the main fluid passage, and an intermediate flexible member fluidly connecting the first side arrangement and the second side arrangement, and wherein the auxiliary flow member is adjustable to a plurality of heights relative to the trapway member, and thus the defined level of the sump water maintained by the auxiliary flow member is adjustable between a plurality of levels, or wherein each of the first side arrangement and the second side arrangement includes multiple flow members (142a, 142b, 144a, 144b), one or more of which can be installed or uninstalled therefrom to adjustable the auxiliary flow member in the plurality of heights relative to the trapway member, and thus adjust the defined level of the sump water between the plurality of levels. - a horizontally positioned trapway member fluidly connected in an installed state thereof between the toilet bowl and the drain line, the trapway member defining a main fluid passage therethrough; and - a valve member installed within the main fluid passage of the trapway member, the valve member is capable of being adjusted between an open configuration and a closed configuration, wherein in the open configuration the valve member allows contents in the toilet bowl to flow to the drain line through the main fluid passage of the trapway member, and in the closed configuration the valve member restricts the contents of the toilet bowl from flowing to the drain line through the main fluid passage of the trapway member, wherein the main fluid passage includes a first flow region defined on one side of the valve member and fluidly connected in the installed state thereof to the toilet bowl and a second flow region defined on other side of the valve member and fluidly connected in an installed state thereof to the drain line, wherein the trapway arrangement further includes an auxiliary flow member defining an auxiliary fluid passage, the auxiliary flow member mounted on top of the trapway member, and fluidly connecting the first flow region and the second flow region of the main fluid passage, wherein the auxiliary flow member includes a first side arrangement fluidly connected to the first flow region of the main fluid passage, a second side arrangement fluidly connected to the second flow region of the main fluid passage, and an intermediate flexible member fluidly connecting the first side arrangement and the second side arrangement, and wherein the auxiliary flow member is adjustable to a plurality of heights relative to the trapway member, and thus the defined level of the sump water maintained by the auxiliary flow member is adjustable between a plurality of levels, or wherein each of the first side arrangement and the second side arrangement includes multiple flow members (142a, 142b, 144a, 144b), one or more of which can be installed or uninstalled therefrom to adjustable the auxiliary flow member in the plurality of heights relative to the trapway member, and thus adjust the defined level of the sump water between the plurality of levels.