Pond Boss Forums POND CONSTRUCTION Renovating a Pond or Lake? How to drain a large pond to do a repair? Ideas?

I have a 1.1 acre, 2.9 million gallon pond. I need to repair a submerged pipe and valve, 2-3 feet below surface. The pond level won't naturally lower until Fall. There is no provision to drain it. I need to do this repair before spring.

I have a Honda gas operated water pump. It uses about a 3" inlet and 3" outlet. But that seems puny given the pond size?

Or, I might be able to rig up some flex hose or 4 or 6" PVC, and prime a suction from out of the pond? I'm hoping I can time this between storms this winter, so rain is not filling it as I am draining it.

Any ideas? I've never tried to do anything like this!

Is the current water level above an area outside of the pond that is a lower level? I assume there is because you can't pump it and have it coming back in the pond. So if there is an area that is lower, I would siphon it to start of with. Take that down as much as it will. Then I would pump it, if needed at that point.

i bet that 3 inch pump will lower it 2 inches or better a day. rig up a 5 gallon bucket as an auxiliary gas tank.

I would get some 4 inch thinwall PVC and ells as necessary, and glue it up to be a siphon over the pond bank. Then I would use the the gas pump to fill the pipe and start the siphon. Corrugated pipe is so hard to seal at the joints, that I doubt it would maintain a siphon due to air leaks.

+1 The 3 inch pump I rented when I dug my pond pumped around 18000 gal/hr. If there is no significant water flowing in, a good 3 inch pump should drain a 3 million gallon pond in around a week or so if kept full of gas.

True, but 4" thin wall PVC is fairly cheap and a siphon will drain without fuel or attendance. If the water level is at least 3 feet above the ground level below the dam, the siphon will do the trick. He only needs to drop it three feet.

Good point John. Those siphons are definitely fuel efficient! If he took the time to set it up correctly, he could make it permanent and use it as an emergency spillway as well. That's what I would do if I had a lower area I could siphon to.

Billy,

What is the purpose of the submerged pipe and valve you want to repair?

There is a dam along one side of the pond, and fairly steep. At the edge of the dam is the spillway, also with lowering terrain for good outflow.

I think I need to look at the 4" thinwall pvc idea. My water pump only has about a 1 gallon gas tank. If it would need 24 hours to drop two inches-- yikes! No sleep ha ha.

The valve is part of an irrigation system. It was damaged but never repaired. Next spring, when I want to pressurize the irrigation (gravity flow) this broken pipe/valve will be compromising that. At a minimum I just need to cap the pipe and do a full repair in fall when water levels are down. I'm also considering digging along the shore to find it and cap it ... out of the water. Of course, there are no plans whatsoever .... so I'd be having to guess where to dig.

If doing a siphon drain, thinwall might collapse, and the belled ends might not seal 110% allowing air into the system and breaking the siphon unless they were silicone sealed together.

I have a 3" Honda trash pump. I disconnected the gas tank that came with it and use an outboard motor gas tank sitting on a 5 gallon bucket next to the pump. Gravity feed from the outboard tank, not a suction feed. A 6 gallon tank will run the pump for close to 18 hours running wide open, and almost 30 hours at half throttle. I use semi rigid suction hose, 4" flex "roll flat" hose to get to the top of the pond basin, then 4" (Not 3") belled thinwall sewer pipe to get the water away from the pond. Some discharge runs are in excess of 150 feet, and by using 4" discharge on a 3" pump, and having the pump as close to the water level as possible to push water not suck it, I surpass the rated GPH discharge of the pump.

When I say thinwall, I am referring to SDR35 or DWV, but they are not interchangeable. Both are somewhat thinner and lighter than sch 40. Four inch sch 40 is kind of a beast to handle.

I used 30 feet of glued SDR 35 through my dam as an inlet pipe (above max water level) and it works great. I buried it at a maximum depth of 31 inches in the clay.

I used 10' sticks of 2" sch 40 pvc with rubber couplers and drained a 9' depth .3 ac pond in 5 days with zero supervision. 10' 2" pvc sticks are light and manageable. Entire rig was under $100 and I was able to break it down for easy storage - no glue no hassle no worries.

Consider a roll of 2" poly for a siphon.

https://www.menards.com/main/outdoors/wa...44431568213.htm

teehjaeh57: did the rubber couplers you used leak at all? Were the connections "fragile" in any way? I was thinking about using that type of siphon system to send water to a cattle trough/stock tank at the bottom of a long and steep dam.....that 2 inch PVC would (in my mental plan)dead-end at the stock tank and the water flow would be controlled by a shut off valve float in the tank.

I think that would work as I want to fence out the cattle from this particular pond so I can improve the water quality. This siphon system would only be up and running when the cattle are out on that pasture and the temps are above freezing. BM61.

I agree with the PVC siphon system. You must glue the pipe or use the rubber boots with the hose clamps. Do not try to use the solid corrugated drain tile pipe, it has small pin holes in it. Even the smallest hole will eventually cause the siphon to break and stop flowing. I'm speaking from experience here, finding the pin holes and plugging them took more time than I'd like to admit to.

Rubber couplers worked great, 100% seal, and allowed me flexibility glued pvc would not. Easy to disassemble and reconfigure for other ponds with different depths and geometric configurations. Entire system fits easily in truck bed.

2" ball valve on back end, top [through which you fill siphon] and pond end. Below the ball valve on the pond side I go down another 5' or so with a T and 2 5' sticks capped with 1/2" holes drilled. This prevents any fish/turtles from being stuck in the siphon which has happened to me several times draining ponds.

Design was simple enough for me to construct, deploy, take apart and store solo. Couplers are cheap and most of the PVC I had on the farm already. Rex helped a lot with this configuration - thanks Rex!

Thin wall S&D pipe will collapse on itself with only a 5- 6 foot lift of water if there is even the slightest bend in the pipe. The S&D pipe is not intended for any pressure (high or low).

For 1.1 acres, go with 4" schedule 40 pipe with rubber couplers and be sure to make a strainer for the inlet so fish, turtles and sticks don't get sucked in that could cause a clog. 2" pipe would take a couple weeks or more to drain, where 4" will lower it in a day or two. Also, use a 45 degree elbow pointing upward on the outlet so air cannot creep up the discharge pipe and break the siphon.

Ball valves are cheap for 2"....not so cheap on 4" so forget about a valve on the pond side and use a "Test Plug" instead, on the outlet side instead of a valve. (Be sure to stand back fast after filling the discharge side of the pipe when you pull the test plug) Test plug

He's only draining 2-3' depth so I would stick with 2" much lighter and cheaper.

One more question please teehjaeh57: did you need to use any PVC elbows in your system? For instance when your PVC pipe runs out of the pond and up then over the embankment, then over and down the dam side? It would be great if the rubber couplers flexed enough where a PVC elbow was not needed as I would think any elbow would need to be glued. How did you handle that? I hope my question makes sense.

I am guessing you could make some short PVC pieces with elbows that give you the ability to move it to other BOWs with slightly different dam sizes, freeboard heights, etc. The portability factor is important for my intended application. Thanks again for the info. BM61

I did use a 45 elbow at front and back of dam to relieve pressure off the couplers but not sure this was necessary. I only used 2 tee sections - one for top of dam where ball valve was attached and one at pond end of siphon for my 5' capped sticks with holes drilled per Rex to prevent fish or turtles from clogging suction. The rubber couplers may allow one enough play not to use elbows, I just didn't want to risk it. All those parts [pvc, elbows, couplers] are so cheap in the 2" size I didn't have the cost issue of requiring one to cut corners and take chances.

Here's my plan. 4" sch 40 from underwater to over dam. 4" thinwall on drain side. 4" tee underwater, 5 foot horizontal pipes capped and drilled with 1/2" holes. Set at 4' depth. Discharge to have 45 elbow and short riser.

At water edge, pump connected to 4" tee, for filling and priming the 4" pipe. Ball valve on inlet tee and at water edge. All connected using rubber coupler except the underwater tee (I will glue that.)

Operation: Valves open. Start water pump, fill all piping. Turn pump off, simultaneously shutting valve on inlet tee. Drain to desired level then shut off tee at water edge.

Did I miss anything? And do you think the gas powered water pump might break the 4" thinwall-- unless I am really careful (or lucky) to quickly shut it down once the pipe is filled?

No, a 3" pump will not break 4" thinwall. The bigger pipe will lessen the pressure if pipe is open. Unless you open the valve at the lower end you will not be priming the siphon due to airlock.
Most thinwall I have seen is rated for 80 PSI. In my experience, the rubber couplers will slip off at anything above 30 PSI. I have tried them. I wound up using compression couplers.

teehjaeh57 has the right idea. Its exactly how I drain my 2.5 acre pond with 7 springs running into it. It's a one person job takes me about 3 five gallon buckets to fill the pipes to get it started. There is actually a youtube video that shows how to do it as well. I'm sure any size pipe will work. I think mine is 2 or 2 1/2 inch pvc.

https://www.youtube.com/watch?v=8rgpRJ1xCeM

If I was going to build a permanent system I'd go with larger PVC and PVC couplers - since I needed a mobile siphon for several ponds the rubber couplers were perfect for me.

Mine isn't permanent either. I only use mine to drain when I need to do maintenance or something of the sort. When not in use I keep it stored out of the way. I was just posting a link to that video as its a good visual of how it works and is designed sometimes that makes it easier for me anyways to understand something. I didn't notice if the one in the video was permanent or not.

The one in the video used rubber couplings and was on top of the ground so did not appear to be permanent. To my mind, permanent means glued couplings and buried.