Overhead Water Tank (OHWT)
An elevated storage tank, usually at terrace level, feeding the building by gravity.
On an actual building
It sits above occupied space, so leakage shows as damp on the structure below rather than as a visible drip. The wall-to-base junction cracks most often, because that is where restraint is greatest.
What we most often have to correct
That any waterproofing coating will do inside. Potable storage needs a certified food-grade lining.
Where this comes up in our work
Terms that come up alongside this one
- Underground Water Tank (UGT)
A below-ground storage tank, usually the building's primary water store, filled from the mains and pumped to the overhead tank..
- Food Grade / Potable Certification
Certification that a lining material is safe for contact with drinking water, issued against a recognised standard and valid for a stated period..
- Fillet
A curved or angled cement mortar profile formed at an internal angle so that a waterproofing layer turns the corner on a curve rather than a sharp right angle..
More building elements terms
Overhead Water Tank (OHWT) — questions we get asked
What does overhead water tank (ohwt) mean in waterproofing?
An elevated storage tank, usually at terrace level, feeding the building by gravity.
Why does overhead water tank (ohwt) matter on a real project?
It sits above occupied space, so leakage shows as damp on the structure below rather than as a visible drip. The wall-to-base junction cracks most often, because that is where restraint is greatest.
What do people commonly get wrong about overhead water tank (ohwt)?
That any waterproofing coating will do inside. Potable storage needs a certified food-grade lining.
Have a building showing this?
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