Emptying pressure pipe

[MartinLe]

Three submersible pipes in paralell will feed a pipeline, lifting wastewater by about 7m and feeing into a tank (near the bottom). Sveveral instruments will be installed along the pipe, including a static mixer, flow meter, etc. I think it would be a good idea to be able to empty the pipe.

The medium is water, main pipe will be DN300.

There will likely be one high point, but no low points along the pipeline.

My first idea is to have a small ball valve at the manifold or similar to empty the pipeline into the sump. This seems straightforward, but I've never seen something like this, is there any problem with such a setup?

I'm not sure about the high point. Vacuum breaker valve? Smallish pipe with manual valve and open end straight upward? Take extra pains to avoid the high point (my curent preferred option)?

My problem with the vacuum breaker is that I have zero experience with these and that I want to avoid aditional maintenacne points. My problem with the second option (and maybe with the vacuum breaker, too) is that right now I have no place to put the pipe two where I can tolerate spillage and that's frost free. Any thoughts or aditional questions I should consider?

 

[LittleInch]

I'm not really following this post and a profile drawing would help a lot.

If you have a high point then at some point you have a low point. Unless your pipe is absolutely horizontal??

Why is it a good idea to empty the pipeline? once full of your waste water with things in the line like a mixer, it becomes impossible to pig it . so draining at the low points is your only answer.

Vacuum breakers can become corroded and break if you don't use them a lot.

how often do you need to drain the line?

If rarely then just add a vent / air relief manual valve.

BTW what is meant by submersible? Are these under water in a river? the sea?, a lake?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Artisi]

More pump detail would help.
Wet pit or dry pit?

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[MartinLe]

Submersible pump means the pump is submersed in a wet pit. The low points are the pumps at one end and the discharge into the reactor at the other. There are no other low points.

The medium is wwtp discharge.

The pipe will need to be emptied maybe less then once a year. Together with littleinchs hint about corrosion the breaker is ruled out.

Since asking the question I've seen on pictures of another similar installation that they had a ball valve on the manifold to empty the pipe (and manual valves at the high point) & the operator had no complaints about the setup.