Practical Cisterns Buying Guide
Quick Answer
A cistern makes sense once water needs go beyond what a rain barrel can practically hold — but the choice between above-ground and underground installation depends more on available space and budget than on which is objectively “better.”
Above-Ground vs. Underground Cisterns
- Above-ground cisterns: considerably cheaper to install since they avoid excavation, but take up visible yard space and need frost protection in cold climates.
- Underground cisterns: preserve usable yard space and stay naturally insulated from freezing, but installation costs are substantially higher due to excavation and structural requirements.
Sizing Based on Roof Catchment
A cistern’s practical size should relate to both the collecting roof area and realistic water usage, not just “as large as the budget allows” — an oversized cistern for a small roof catchment area may rarely fill completely, while an undersized one for a large roof wastes collection potential during heavy rain.
Filtration Before Storage
A first-flush diverter, which discards the initial, most-contaminated runoff from a rain event before it enters the cistern, meaningfully improves stored water quality compared to a system with no pre-filtration at all.
Overflow Planning
A cistern will eventually overflow during heavy rain regardless of size — planning where that overflow water goes (away from the foundation, ideally into a rain garden or drainage swale) prevents the cistern from creating a new water problem while solving the storage goal.
Extraction Method
A simple gravity-fed spigot works for basic garden watering from an above-ground cistern, while underground systems generally need a dedicated pump to bring water back up to usable height.
Bottom Line
Above-ground cisterns suit budget-conscious setups with available yard space, while underground systems preserve space at a real cost premium — a first-flush diverter and planned overflow routing matter for water quality and problem prevention regardless of which type is chosen.
