The London Basement Project Estimator
Turn one giant plumbing quote into a realistic after-grant, after-tax number. Select the items in your package, enter the pre-tax quote, and see how much the City pays versus what actually leaves your bank account.
Estimate Your True Out-of-Pocket Cost
Ontario HST is added to your bill, while the City grant is calculated from the tax-inclusive eligible total.
Selected Grant Buckets
Paying too much out of pocket? Get a second opinion from a vetted local plumber.
Bundle Quotes Are Hard to Read
A single $8,000 to $12,000 quote can hide three separate grant caps. This estimator rebuilds the cap total from the work you select.
HST Changes the Real Number
The homeowner sees the tax-inclusive invoice. That is why the estimator adds 13% HST before applying the 90% grant rule and hard caps.
The Red Zone Matters
Once the City grant hits the selected cap, the green bar stops growing and extra invoice increases land on the homeowner side.
Need the quote formatted correctly?
The calculator only helps if your contractor's quote is itemized the way the City expects. Get the checklist before you submit anything.
Download the Free Grant ChecklistHow the Basement Flooding Grant Math Actually Works
When you receive a quote from a licensed plumber for basement waterproofing in London, Ontario, the sticker shock can be intense. However, the City of London's Basement Flooding Grant Program is designed to absorb the vast majority of that cost.
Our project estimator above uses the exact formulas mandated by the City to help you calculate your true out-of-pocket expense. Here is a breakdown of the rules we use to calculate your estimate:
1. The 90% Rule vs. The Hard Caps
The City promises to cover 90% of your eligible construction costs. However, they place strict maximum limits (caps) on every piece of equipment. If 90% of your plumber's invoice is higher than the City's cap, you only receive the capped amount.
- Backwater Valves: Capped at $1,800 maximum.
- Sump Pits & Pumps: Capped at $4,000 maximum.
- Battery Backups: Capped at $1,400 maximum.
2. Factoring in the Ontario HST
One of the most common questions homeowners ask is: "Does the grant cover the taxes?" Yes. The City of London calculates your 90% reimbursement based on the final, tax-inclusive total of your invoice. Our calculator automatically applies the 13% Ontario HST to your base quote to ensure your out-of-pocket estimate is accurate down to the penny.
3. Multi-Item Bundle Quotes
If your home requires both a backwater valve and a new sump pump, your contractor will likely issue a single, bundled quote. To get approved, that quote must be strictly itemized. The City will apply the 90% rule to each item individually against its specific cap. Our tool allows you to toggle multiple devices to simulate this exact bundled calculation.
📍 Avoid a Denied Application: If your plumber does not format your quote correctly, the City will reject it, leaving you to pay 100% of the bill. Download our grant application rules guide to see exactly what your invoice needs to look like before you submit it.