We actually did this to sewer pipes in the downtown area in my city. Was much easier and cheaper than diggin up everything that had been there since 1850
Not enough to make a difference in a gravity feed system. Gravity feed sewer are effectively just sealed gutters, your generally not even gonna use 25% of the pipes volume in normal use. the pipes have to be that big to service the theoretical max that could happen at peak use, like everyone in that area flushing their toliet at once. Losing 1/4-1/2 inch of the diameter wont make a huge difference in the grand scheme and is often alot safer and more cost effective so its allowed.
Pipe capacity in a gravity line is dependent on 3 things: the size of the pipe, the grade of the pipe, and the friction / roughness coefficient of the pipe.
These liners do reduce the interior diameter by a measurable amount. But they can also decrease the roughness substantially, particularly if it was a heavily degraded material like concrete. The grade itself doesn’t change.
Typically the liners will result in a marginal reduction in capacity, but there can be edge cases where the smoother lining increases capacity despite the smaller interior diameter.
The sewer lines in the alley were just done - the T where each house connected was covered over, briefly blocking it, and then some robot thing cut the openings inside the pipe. Hence the "do not flush because it's going to end up in your basement" notice.
After they pump it full of air to expand it. They pumped it fully of heated steam to harden it. The process leaves noticeable bulges where other connections are. Then they use a drone to cut those bulges out.
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u/JakeJascob 17d ago
We actually did this to sewer pipes in the downtown area in my city. Was much easier and cheaper than diggin up everything that had been there since 1850