@Njunge,
The tanks are cylindrical ( circular). Purely good workmanship ( skilled fundi, plastering and quality of materials used) and location ( at least away from would be pollutants) ensures no seepage. I did 2 purely due to finances as i did one first and after 5 years did the other one. Size would depend on the roof catchment to harvest the water from and of course finances.
@ GGK
If ur water bills are low like 1.2k it would be better to invest in a good plastic tank as the cost of a concrete tank would far outweigh the benefits. But if you plan to do some kidogo back-yard farming and live in a water scarce region then you could invest in a tank.
If you decide on a concrete tank, i can introduce u to a good fundi.
@ MatataMingi.
Any JuaKali artisan can fabricate the mabati-type gutters. Mine are Jua Kali. There is some company dealing with plastic ones which i hear are long-lasting and easy to clean but i never considered them as i heard they are pricey.
To clean the system, a corked-pipe from the gutter system is fixed to let the first rains just drain away. This is good if all the water drains to the tank from the roof level. If some water is collected through underground pipes, then a man-hole trap just before the water gets to the tank is used collect water from the first rains and then drained.
Hope this helps!
"Things that matter most must never be at the mercy of things that matter least." Goethe