'''Step 9:''' Keep the foundation moist and under shade for 3 weeks
====Leakage through walls without cracks====
[[Image:newly plastered tank.jpg|thumb|right|150px|A newly plastered tank must be cured for three weeks. Photo: © E. Nissen-Petersen, Kenya.]]
'''Problem:''' Water leaks through the wall of a water tank, although the wall has no cracks.<br>
'''Reason:''' The wall is leaking due to porosity caused by either a mortar mixture with insufficient cement, insufficient curing or poor workmanship.<br>
'''Remedy:''' The wall can be sealed by replacing the porous parts with mortar 1:3 and with NIL. Should the wall still leak after that treatment, the interior of the tank should be coated with a water proofer.
'''Procedure:'''
'''Step 1:''' Drain all water out of the tank and clean its interior
'''Step 2:''' Chisel away the porous parts of the interior wall.
'''Step 3:''' Clean the chiseled parts with water and throw dry cement onto the watered parts of the wall.
'''Step 4:''' Mix mortar of 1:3 and throw a thin layer of it onto the watered parts of the wall.
'''Step 5:''' Next day, fill up the coated parts with mortar 1:3 and apply NIL with a square steel trowel. Keep the plastered parts moist under shade for 3 weeks, and then fill the tank with water.
'''Step 6:''' Should the tank still leak, its internal side has to be painted with a water proofer, such as swimming pool paint, non-toxic bitumen, oil paint or 1 part of cement with 10 parts of lime mixed with water.