Sizing Guides
Advice · Sizing
Size it once. Size it right.
Choose by application first, then by capacity. Quick rules of thumb for storage, rainwater harvesting and off-mains supply — and when it’s worth a call.
Start here
Choose by application first
What the water is for narrows the field before capacity ever comes into it.
Drinking water
Any items holding drinking water must of food-grade quality. Non-negotiable for anything feeding a tap and if in doubt, please refer to Drinking Water Standards and Regulations (use link: https://www.dwi.gov.uk/drinking-water-standards-and-regulations/)
General storage
A cost-effective way to store non-potable water for non-drinking uses such as irrigation, washdown, process water. including reconditioned IBCs and tanks. However, must not be connected in any way to the mains without correct backflow prevention in place.
Harvesting
Sizing the adequate storage using roof area and average rainfall in the post code, buffered for dry spells and use case dependent.
Agricultural & commercial
Large-volume storage such as agricultural water, cattle drinking, emergency water storage such as fire and industrial water storage for things such as manufacturing processes.
Rules of thumb
Quick sizing figures
A few things to consider when helping size your project before purchasing —
Match it up
Application → typical capacity
| Use | Typical range | Notes |
|---|---|---|
| Loft cold-water | Our Loft tank range will need to pass loft hatches so check size | Slimline / sectional to pass loft hatches |
| Domestic rainwater harvesting | Above or below ground | Sized to roof area & garden demand |
| Smallholding / stock water | Size and compliancy level if on mains | Above-ground bulk, HIAB offload due to size |
| Commercial / process | Size and compliancy level if on mains | Base loading & access govern the choice |
Common questions
How big a tank for a family of four?
This depends on whether it’s backup storage or full off-mains supply. As a starting point, size on daily use × the days of reserve you want to keep for back up supply however be aware of Drinking Water Standards and Regulations (use link: https://www.dwi.gov.uk/drinking-water-standards-and-regulations/) as to prevent inadequate water turnover
Above ground or underground?
Above ground is cheaper and easier to inspect; underground saves space and keeps water cool. Underground needs groundworks — see installation.
Tell us the job. We’ll size the tank.
Usage, roof area or project detail — whatever you’ve got. We’ll come back with a size and a shortlist.