Honest math
Formulas from BIS IS 15797:2008. Rainfall from IMD normals. Every number sourced and dated.
Capture the rain. Avoid the tanker.
Rainwater harvesting for Indian homes — compare certified installers, financing options, and your state's compliance rules. Free.
Live in KA · TN
54.2k L
captured per year
From a typical 100 m² Bengaluru rooftop
3–5 yr
typical payback
With tanker-bill avoidance + mandate penalty avoidance
₹5,000
BBMP fine you avoid
Up to ₹5,000 + 50% water-bill surcharge in Bangalore
How it works
- 1Tell us about your roof
Address, roof material, monthly water bill, tanker dependence. 60 seconds.
- 2See your harvest
Annual litres captured, recommended system, payback, mandate compliance status.
- 3Pick installer + loan
RWH-certified installers in your DISCOM area + home-improvement loan options.
What you get
Harvest volume estimate
Litres per year, sized to your roof, your material, your district rainfall.
Recommended system
Tank + recharge pit specs, hybrid by default. With cost band.
Mandate compliance check
Are you mandated? What paperwork? What penalty if you skip?
Tanker-bill projection
Tanker spend before → projected after. The biggest economic lever.
10-year cumulative savings
Honest math. No 25-year hype.
Installer + loan compare
IS 15797-compliant installers + 8 home-improvement-loan options.
Why RainbowHome Water
No sales pressure
The calculator runs without an account. You only share contact details if you ask for a quote — consent is never pre-ticked.
One view, all options
Compare installers, loans, AND your compliance status. No juggling 5 quote calls or BWSSB lookups.
Is your water hard, or unsafe?
Bengaluru hard water and monsoon contamination are a different problem from harvesting. Check your area's water quality and get matched to monitoring partners.
FAQ
Is rainwater harvesting really mandatory in my city?
Yes if you're in Tamil Nadu (all buildings since 2001) or Karnataka (new buildings ≥1,200 sq ft since 2009, existing ≥2,400 sq ft). See our Mandate guides for the specifics.
Storage vs recharge — what's the difference?
Storage saves rainwater in a tank for non-potable household use (toilets, washing, gardens). Recharge sends the water into a pit or borewell to lift the groundwater table. Hybrid systems do both — captured for use, overflow to recharge.
Is this free?
Yes. The calculator is free and works without an account. We only ask for contact details if you request a quote from an installer.
Do you sell my data?
No. If you ask for a quote we share your contact with the installer(s) you select — only with your explicit consent, only for that purpose.
How do you pick the installers and loans?
We list every IS 15797-compliant installer active in KA/TN and every bank offering a home-improvement loan eligible for RWH. We rank by price-per-m², warranty, and certification — not by who pays us.
What does RainbowHome earn?
When you pick a partner, we get a one-time referral fee from them. The estimate stays free; you pay nothing extra over a direct quote. Partners commit to passing through the same pricing.
How accurate is the harvest number?
Numbers are derived from BIS IS 15797:2008 (roof area × runoff coefficient × annual rainfall × first-flush and filter losses) and IMD historical rainfall normals. Real-world yield varies with monsoon strength and maintenance.
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