I need to replace the drain pipe in a pond about 3/4 of an acre and I have a question about the new drain pipe. The old pipe is damaged beond repair and is at the bottom of 10ft embankment and I don't have the money at this time to dig the embankment up to repair the pipe. I don't have a need now or in the forseable future to dain the pond completly. I plan to abandon the old pipe and install a new pipe. I will dig a trench 3ft deep and put the pipe in the trench. I'll put a 5 or so degree slope on the pipe so it will be a straight run through the embankment. This will give 2ft of water above the pipe. I'll attach a riser pipe to the drain pipe. My question is what type/material of pipe should I use for the 6" drain pipe, PVC (Polyvinyl Cloride), Corrugated HDPE (high density polyetheylene) or cast iron. If I use corrugated pipe should it be single or double wall, if PVC should it be solid wall or foam core and what SCH 40, 80. I would prefer not to use cast iron unless its necessary. Is there any specification for the pipe to look for. The embankment is 12 - 15ft wide. The winters around here can get down to 5F for a week at a time but the oulet of the pipe will be under a 1ft of dirt. Also with this shallow of a depth does one need to use an antiseep collar. If it matters the old drain pipe was clay and lasted for 40-50 years. Its a long post but I am new to owning a pond and hope to get some advice from people who installed drain pipe in there pond. Any other advice would be appreciated.
todd098, I think sch 40 PVC is pretty standard. I am about to replace my old drain with a siphon drain. You might consider that. There are guys here with vast knowledge in this area. I'm not one of them. They will help you out. What are you doing with the old drain?
I found out the hard way that it's more expensive trying to put a valve on corregated than PVC pipe. I'd lean that way and use what the pocketbook will allow, stronger is always better I say!
NRCS spec's sched 40 for drain pipes. Schedule 80 is spec'd for lines buried beneath 20' + of earth. I don't know that cello core or solid core is much of a difference for this specific application; others may be able to add knowledge.
I'm in a similar situation to Todd and am looking at different options. I have a question....What is the reason for laying the pipe two feet below the water level and then adding a riser? What's the advantage to doing it that way instead of laying it at the intended water level?
1 3/4 acre, 1/2 acre, and 1/10 acre ponds in NE Smith County, East Texas.
The reason I wanted to have the drain pipe two feet below the surface is first the ice on the pond can get up to 10" thick in winter. With the pipe well below the surface I don't have to worry about the water freezing in the pipe. If the pipe is at the level of the pond it acts a a culvert and water may freez in the pipe. I have been online and still haven't found any answer to my question. It seems most of the articels or manual I have read deal with drain pipes in large lakes not small ponds. If I find any good articals I'll let all know. Let me know what you decide to do about your situation.
i think the nrcs may be slightly different here in oklahoma not sure why. they only recommend and will only pay share on sch. 40 smooth steel pipe. they say there records over the past 30 to 40 years proves it last longer than anything. absolutely no pvc or corrugated. they say no to pvc due to sun and fires and no to corrugated because unless its smooth inside it reduces water flow and that water sets on the bottom and rots them out even on a 12 to 1 slope the water sets in the spirals and doesnt drain dry. but i see a lot of folks on here using both which surprised me but it may just be different in different areas. at first i didnt like the steel pipe but i'm kinda changin my mind on it. once in place you can get pretty ruf with it. the nrcs doesnt require us to use a packer but to add 10% for shrinkage using dozer. so once pipe is in we put a couple inches of cover on it and drive over it to get some compaction. you have to be way more careful with plastic.anyway havent had any problems yet and going back to fish some of these ponds that are 10 to 15 yrs old the metal pipe looks almost as good as new. by no means am i sayin using a packer isnt better i think they are trying to keep it cheap and it seems to be working. these pipes may or may not have a riser but they always start at ditch behind pond and come out at desired water level in pond so they are probably 8 or 9' ft deep in places on the dam. and they usually have 2 anti seep collars welded on. hope this helps you a little although compared to some of these other replies oklahoma is a much warmer climate so it may be different here.
as far as the riser question goes here the nrcs recommends it to be twice the size as the drain pipe. one advantage of a riser that i like is that it gets rid of the water faster. with no riser if the pond is an inch full you have an inch going down drain pipe. with riser if the pond is an inch full the tube is runnin full blast so you dont need as much freeboard. if you like this method i will try to post a sample of one of the nrcs plans on this pipe start to finish with riser it might come in handy when your able to drain pond for a permanent fix. will try to post some pictures of pictures as you can tell by my thumb in them of a pond without riser on pipe and another of me building a pipe with riser on it. the one without riser does take much less time
You should also probably avoid corrugated plastic tubing (single or double walled) for two reasons. One is that is actually bouyant, and you need to be careful about ensuring the inlet is held down by a lot of rock covering it. However the bigger issue is that NRCS is starting to see issues with the double walled pipe forming cracks down the length or around the circumference. In SD they recommend schedule 40 sewer pipe.
Tim is exactly right about the reason for using a drop inlet on the tubing. Our bigger dam has a 5 ft diameter rising flowing into a 2 ft horizontal pipe. When 6 inches of water is running into the inlet, the starting part of the 2 ft tube is completely full, but by the time it drops 15 ft to the outlet it is only running 1/4 full (but very fast).
The diameter of your tube is determined by the watershed area, topography, vegetative cover, and 25 or 50 year precipitation events. A 6 inch tube is small and subject to plugging, so I'd recommend at least a 12 inch tube. The pipe won't cost that much more, and installation will be the same.
