How to flush out dirty water after turning off and on the water main?

[ahsiung]

Our four-story apartment building does not have a shut-off valve for each individual apartment. Whenever we need to fix something we need to turn off the water main. Afterward, the water is always dirty. Is there a simple way to flush out all the dirty water by turning on only one unit instead of flushing all the units? My logic says I should flush from the bottom unit. But it did not work.

Thanks.
Ahsiung

 

[Jadnashua]

Pipes usually have an accumulation of crud on the inside. So, IMHO, there's no way to clear it totally from one location. If you did it from the highest location until clear, then only the internal local branches would need to be cleared, taking, probably less water after all.

Water companies periodically try to clear their main lines by opening up water hydrants. You need a lot of flow to actually clean the stuff out of the pipes in your internal piping. Unless you have a full-port valve, you'll probably never get it all out. The act of turning it on and off, when the water fills the pipes back up, it dislodges only a little bit of it.

 

[Sponsor]

 

[hj]

dirt

Turn the water on very slowly so it does not disturb the dirt. The pipe is still full of water so it would not need a lot of time to fill.

 

[ahsiung]

We're thinking of turning on all the lower level faucets before turning on the main - as you suggested, very slowly - hoping that the pressure will not be strong enough to push the dirt to the higher levels and come out on the lower level. What do you think?

 

[Jadnashua]

If the pipes drained, when you turn it back on, it will flow and dislodge stuff...turning it back on slowly with taps open will allow it to fill back up without shocks. But, if it is pressurized with air in it, when you then open a valve, it will dislodge crud as the air is purged out and the pipe refills. It's just something you have to live with. Just like the water company tells people when they are flushing the main lines...you will likely get some crud in your taps, too.