forcemain discharge to pond
forcemain discharge to pond
(OP)
I have a pumped stormwater forcemain that discharges into a pond via a 4 inch pipe above the pond water level. The discharge velocity is so powerful that it shoots the water about 10 feet at a fairly high pressure and has started to erode the pond bottom. I have been tasked with fixing this issue. I don't know the flow and the pressure in the forcemain and the pump is constant speed. I am thinking just to increase the last 20 feet of pipe to 18 inch diameter or so to slow the velocity down to basically a standstill and then the water will just fall immediately into a rip rap basin. Do you think this will work or do I need something like an orifice plate in the line as well to reduce the pressure? Any help is appreciated. Thanks.





RE: forcemain discharge to pond
an orifice plate will reduce the flow and increase the pump head, probably not useful. 18 inch is probably too large, you need to maintain a minimum velocity of about 2 or 3 fps to move solids. the most common solution is to discharge into an energy dissipater instead of just shooting it into the pond.
RE: forcemain discharge to pond
RE: forcemain discharge to pond
Another option is to turn discharge up and create aerated discharge...helps for a variety of reasons.
RE: forcemain discharge to pond
What is usually used in this application is a simple multi-port diffuser. You can fabricate a 4-Inch submerged diffuser 5-6 feet long that should be comprised of approximately 10 ports with each port being a 2-Inch diameter pipe. Attach the submerged diffuser onto the end of the existing pipe.
If you have about 250 gpm in the 4-Inch pipe, that will give you a velocity of approximately 2.5 ft/sec out of each of the diffusers.
Here is a link to examples.
http://www.cormix.info/CORMIX2.php
RE: forcemain discharge to pond
RE: forcemain discharge to pond
RE: forcemain discharge to pond
RE: forcemain discharge to pond
Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East - http://www.campbellcivil.com
RE: forcemain discharge to pond