The ornamental design for a watertank for airpurifier with humidifier, as shown and described.
1. Water tank for air purifier with humidifier
1.1 is a perspective view of a water tank for air purifier with humidifier showing our new design;
1.2 is a front elevation view thereof;
1.3 is a rear elevation view thereof;
1.4 is a left-side elevation view thereof;
1.5 is a right-side elevation view thereof;
1.6 is a top plan view thereof;
1.7 is a bottom plan view thereof;
1.8 is a perspective view thereof showing its handle in a use condition; and
1.9 is a perspective view thereof showing the combined air purifier with humidifier in a use condition.
The broken line showing in 1.9 is for the purpose of illustrating environment of the water tank for air purifier with humidifier and forms no part of the claimed design.