Pond Boss Forums GENERAL QUESTIONS Property Projects & Construction Pond Drain

I am constructing a 3 acre pond where 50% of the area will be 20 to 25 foot deep and the remainder 8 to 18 foot deep. My plan for a drain (ability to completely drain the pond if I need to) is a gate valve for a pipe that runs horizontally through the dam just 18" above the pond bottom. What diameter PVC pipe should I use if I want to be able to drain the pond completely within 48 hours?Thank you!

I use 8 inch PVC and 6 inch PVC in all my ponds with gate valves on the outside of the pond dams. Reason for the size is cost of product and access to the supply. I have drained my ponds and I am usually not in a big hurry. One of the engineering fellows will have to calculate the head and volume for you to size the pipe for a complete drain in 48 hours. I have seen some tables in some of the engineering books that I have had at one time but dont remember where. I usually purchase my pipe and valves from the same supply company that supplies our local water board their products. I always use PVC. I have observed a lot of failures in older ponds here that belonged to neighbors and family members that used metal pipes in their ponds.

SGF, given those figures, a WAG is that you have to move around 712,799 gallons per hour. I would call Pond Dam Piping and see what they recommend. They will probably need a bit more information such as length of pipe, etc.
Taken from the resource guide:

Contact:Keith JohnsonAddress:398 Eighth Street
Macon, GA 31201Phone:(478) 742-0003 Toll Free:(800) 333-2611 Email:[email protected]
Website:ponddampiping.com

Or, if you want to plug in the numbers yourself, go here: http://www.ercp.com/catalog/design/hydraulicdesign_culvertdesign.htm

Thank you. I spoke with Keith, and he was very helpful. He recommended the more expensive design of placing the valve on the pond side of the dam, but did not have any advice on pipe diameter.

Richey,
This pond will be 20 foot deep at the dam. Consequently, if the gate valve is on the outside of the dam (the dry side of the dam), then the pipe will have continuous internal pressure from that head of water.
Have you had any concern with the drain pipe staying under pressure inside your dams?
Do you take any special steps to seal these pipe joints that are inside the dam?
Thanks. SFG (first pond)

SGF, if you follow the link that I posted, you should be able to plug in numbers that you generate from the dimensions of the pipe (length and depth that it is underwater, or head pressure) and get the size pipe you need.

If it was me, for a WAG, I'd average out the head pressure at 10'. It'd flow more at higher head, and less at lower head.

Diameter will depend on length of pipe and # of gallons per hour. To get you a jump on the numbers, there are 7.48 gallons in cubic foot.

While it's more $ up front, I agree with having the valve on the pond side of the pipe.

While it's more $ up front, I agree with having the valve on the pond side of the pipe. [/quote]

Esshup, Mine is on the outside of the dam. Just curious what is the benefit to being on the pond side.

With the gate on the pond side, if there's any pinhole in the pipe, it won't be constantly leaking into the dam. Plus, with the pipe on the bottom, it's under more pressure than if it were on the top of the water column.

Personally, if I were doing it for my pond, I'd look into a siphon system, running near the top of the dam.

drain thought stimulator

Esshup, Thanks for the response.As I stated I bought my place so it is what it is. I did cycle it just a few days ago to see if it functioned (it did thank goodness) From what the previous owner described it is installed similar to "Brettski's" setup although I'd venture to say with nowhere near the detail on the pickup end. Which by the way Brettski excellant write up in the "drain thought stimulator"