Backwater valve in Welland: the Building Code and the permit fee.

The Ontario Building Code, not the SWAP program, is why a backwater valve is required at all. The City's own plumbing fee schedule, not the SWAP page, sets what the permit for this work costs.

What the Code requires, and what it does not

Article 7.4.6.4 requires a backwater valve wherever a fixture sits below street level, or, for a home on a public sanitary sewer, below the upstream sanitary manhole cover. That rule reaches most basement fixtures on a sewered Welland lot built to today's Code. For an existing, older home, nothing in the Building Code compels a retrofit: the Code attaches to construction and permitted plumbing work, not to a house standing untouched. That is the honest reason an older Welland home installs a backwater valve today: the SWAP rebate is the reason, not a Building Code order.

Semi-detached homes need one valve per side

A normally open backwater valve may not serve more than one dwelling unit. A semi-detached property is two dwelling units on one lot, so each side needs its own valve; one valve cannot protect both halves. This is a Code requirement, not a SWAP-specific rule, and it is not stated on the main SWAP page.