Any of the following conditions specified in the plans and specifications of any improvement district heretofore or hereafter formed imposed upon the respective parcels of land in the improvement district are binding and may be enforced:
(a) Limitations, based on the amount of assessment in the respective parcels or otherwise on:
(1) Number of outlets;
(2) Number of services;
(3) Number of connections with the improvement district pipe line;
(4) Uses to which water may be put;
(5) Quantity of water that may be used.
(b) Increases provided for as to any of the foregoing on condition that specified tolls, connection charges, or additional assessments are paid.