Water tanks: types, sizes and what to check

What a water tank is for

A water storage tank keeps a reserve of water on site: on a stand or roof to feed taps by gravity, on the ground next to a pump, or below ground. The size depends on how long the house has to run without supply, and the type depends on where the tank stands and how much it has to hold.

Types of water tanks

Types of water tanks

Type	What it is	Size range in the source
Polyethylene (poly) tank	one-piece moulded plastic tank; double layered in Lodhia’s range	500–10,000 L for Lodhia Tritank
GRP sectional tank	glass-reinforced plastic panels of 1 m, bolted together on site	from 1,000 to over 4 million L
Underground water tank	a tank set below ground level, filled from the roof or the supply	depends on the make
Pressure tank	a small sealed vessel on the outlet of a pump that holds water under pressure	sized to the pump

GRP panel tanks cover volumes far beyond a single moulded tank. Tricel’s panels arrive separately and are assembled by trained fitters, and tanks set outdoors need insulation and weatherproofing, the maker notes.

Polyethylene water tank sizes

Lodhia publishes the dimensions of each Tritank size. The diameter tells you the base you need; the height tells you whether the tank fits under a roof or on a stand.

Polyethylene water tank sizes

Capacity	Diameter	Height
1000 L	1070 mm	1300 mm
2000 L	1380 mm	1610 mm
3000 L	1580 mm	1800 mm
5000 L	1870 mm	2070 mm
10,000 L	2340 mm	2590 mm

Other brands, such as Kiboko tanks, use other moulds, so check the figures of the tank you actually buy.

What to check when you buy a water tank

1. Layers. Lodhia describes its tanks as double layered, coloured outside and white inside, rotationally moulded and UV stabilised, in black, blue, green or white. Ask how many layers a tank has and what colour the inside is.
2. Material. The same maker states 100% virgin linear low-density polyethylene and a tensile strength of 17 MPa. A maker that gives no material grade cannot be compared.
3. Drinking water. Lodhia states that Tritank is suitable for food contact; that is the maker’s claim, and other brands should say the same in writing if the tank will hold drinking water.
4. Installation guide. Lodhia refers buyers to its Tritank installation booklet for handling and setting up the tank. Ask for the guide of the make you buy before building the base or stand.

Pressure tanks for a water pump

A pressure tank is not a storage tank. The extension guide on pressure tanks from Alberta Agriculture explains that it keeps the system under pressure while the pump is off, so the pump does not start every time a tap opens. It describes three kinds:

• Plain galvanised tanks with a cushion of air over the water. The air slowly dissolves, and the tank becomes waterlogged.
• Float tanks, where a float separates water and air; they need recharging with air about once a year.
• Diaphragm or bladder tanks, with a sealed air cell, so air and water never meet and the tank should not need recharging.

The guide sizes the tank so the pump starts no more than 25 times an hour, and it sets the air charge 3 to 5 psi (about 21–34 kPa, our conversion) below the pump’s cut-in pressure.

Water tank prices and lined ponds

Tank prices listed by sellers in Tanzania, with dates, are on the water tank price page. Kitovu does not sell water tanks.

For larger volumes stored in an earth pond or a water pan instead of a tank, Kitovu stocks HDPE Geomembrane (Dam Liner), Smooth, 0.3 mm in Zanzibar, an HDPE liner for ponds, water pans and reservoirs. Tanks for sewage rather than water are a different product: see septic tanks and biodigesters.