Once the DSSP is designed and approved by the City department that regulates the storm water, the builder will get the bad news that he needs to specify the SVHV, or the hyrdrovex regulator. This is a proprietary instrument, and used to be made in Quebec by http://www.johnmeunier.com, this company has now been sold and is called http://www.veoliawatertechnologies.ca/en/
For a video on what this looks like, click on https://www.youtube.com/watch?v=giEpL3uBkZY
I am guessing that John Meunier extracted a lot of money from the builders over the years, and happily retired himself by selling his company to a big operation. No doubt the corporate entity that bought out old John has since jacked the price of the valve even more. I wouldn't know the actual price right now because I have not specified any since 2015.
How I undermined John Meunier - The last time I was building a project with a DSSP (2015), I was discussing how overpriced all of the supplies were with my install contractor, at the time I was using a certain excavator with a lot of contacts in the industry. He said he knew of a bankruptcy sale where I could get my hands on a few SVHV's for a good price. I went to the wholesaler, and I bought three of these items, for about $1000. At the time they were selling for more than $1500, so I was happy to buy a few and store them for later use.
This is what one looks like
The vortex regulation effect of the SVHV
This section drawing shows the SVHV at work, allowing water to flow into the storm sewer
The problem with this device is the City started specifying them but there was only one supplier. This is typical of the City, it doesn't care about how much the consequences of its decision that it enforces will cost the builder. Enjoying his monopoly power, John Meinuer, or, as spell check likes to auto correct to, John Meany, was making a lot of money on these items. I have since learned there is a different flow restricting product on the market now that is much cheaper, so, I can officially say, John Meany, you can kiss my ass, you won't be getting any more money from me..