Hi I don't know wtf I'm doing please help
We have a 30+ years old underground sea water supply network that consists of a 20" cement lined CS header and multiple underground branches 8" in size of the same material.
Only at the end of the branch does the line come above ground and a gate valve is placed near the user (exchanger).
As I said this whole network is 30+ years old and now we're facing many leaks from the branches specifically. Replacing the whole network (including the header) is out of the question as it is too big a project, and our main problems are with the branches anyway we rarely (like never) get leaks from the header itself.
Is it worth it to replace the branches? also if we're excavating to replace the branches is it also worth it to move the branch isolation valve to as close as possible to the header? because in current design if the valve is closed for any reason (such as to take user equipment for maintenance) then an "operational deadleg" is created since the water in the branch up stream of the isolation valve is stagnant?
Is it worth to put the valve underground near the header and create cement pit/housing for it? we have 14 branches like this (supply and return are close to each other so 1 pit for both so we only need 7 pits)?
ALSO why did the original designers of this place create it like this? is there wisdom behind what they did? from what I understand they were a very respected engineering company that never cut corners pls help I don't know wtf I'm doing but I feel like something has to be done.
Also if I don't take action now then the next window to do anything about it is in 10 years time.