The Mysterious Depths of Plumbing

One of the first setbacks we've faced in the construction of the brewery has been whether the existing sewer drain running through our space was deep enough. Breweries need drains and taprooms need extra restrooms - all of which need to connect to a sewer line. The depth of the main sewer line running through the space determines how far away these other drains can be placed.

The depth of the main sewer line plays a big factor in designing a space because the new drain lines in the floor must be pitched to allow for proper drainage to the main sewer line. The pitch is usually one quarter of an inch for every horizontal foot of pipe. So if the main line only went down 5 inches beyond the minimum depth according to building codes, you can theoretically only place a drain a maximum of 20 feet away.

Our space currently has two small restrooms, and it was assumed the sewer line was running through the space near those restrooms. The traditional method of determining sewer line (if building records are not available with those specifications) is to manually break up the floor and keep digging to see how far the pipe goes down. We were about to proceed with this method when our landlord mentioned he has another tenant, National GPR Service, that performs ground penetrating radar mapping of floor utilities.

Ground penetrating radar is essentially an industrial strength ultrasound device that scans the floor to determine presence of utilities such as drain pipes as well as their approximate depth. Since this is non-invasive, and (in our case) would be about the same cost of digging up the floor to manually check drain depth, we decided to give it a shot.

On the day of service, the National GPR technician set up and was finished within an hour. He scanned a small area where we thought the drain would be. A drain was found on radar at 5" below an area close to the restrooms and 7" below a little further away. Unfortunately, GPR is not used to determine diameter of the pipe, something that we needed to know and didn't realize wasn't a possibility with this survey method.

Marking of a 7 inch deep drain line found on radar.
Marking of a 7 inch deep drain line found on radar.
Marking of a 5 inch deep drain line found on radar.
Marking of a 5 inch deep drain line found on radar.

Depths of only 5-7" for a sewer main were shocking. It's not even to code. At that rate of incline, the pipe would have been above ground in the neighboring space in our building (it wasn't). Because of this, we realized we would need to get manual confirmation of the depth.

Last week, our contractor, architect, and a plumber met us at the space. After discovering there was already a capped drain in the warehouse area of the space, the plumber removed it and dropped a tape measure down. To our relief, it showed a 4 foot depth and was also 4 inches in diameter.

The main sewer drain in our space drops 4 feet before turning horizontal to run through the rest of the building.
The main sewer drain in our space drops 4 feet before turning horizontal to run through the rest of the building.

It turns out that the pipe the National GPR technician mapped out was an accessory drain running from the existing restrooms to the main sewer line. The GPR equipment the technician had available can only determine what is within a few feet of the surface, so it wouldn't have been able to map a 4 foot drain line, anyway.

Because of the depth, we now have much greater flexibility in the placement of drains through the space, freeing up our architect to focus on a layout that enhances the taproom experience the most. If it hadn't been deep enough, we were faced with the possibility of having to run a new sewer line from the main line in the street - a project that probably would have set us back $10,000-15,000!

Additionally, the diameter of the sewer pipe is very important. Anything less than 4 inches is usually not adequate depending on the local building codes. If our main sewer line had been less than 4 inches in diameter, we would have likely needed to run a new sewer line from the main in the street.

Fortunately, the outcome of this setback was positive because we don't have to install a new sewer line. But it did set our timeline back about 2-3 weeks, and we'll end up paying more rent before opening because of this. When choosing a space for a brewery, make sure to add checking the sewer drain location, depth and diameter to your list of due diligence items before signing the lease agreement.

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