FlexPVC Bog - Drilling vs Cutting

[frogbath]

So I've started to work on the bog plumbing and after reading a few threads here decided it would be most efficient and reliable to have a "straight" run of flexpvc from the pump in the vault of my intake bay up and into the bog. I've got a clean out and cap on the end and plan to run it along the bottom of the bog and just flex it a little upwards towards the end so I could easily dig out the clean out if I ever needed to.

I've read some threads that say slits are best to prevent clogs, others say drilling holes is fine so long as you make them large enough. I have a triangle step drill reamer bit so I'm not too worried there. Given that only water is going to be making its way into the bog because the pump is under my intake bay I'm not too worried about clogs (maybe that's dumb cause algae etc?) but I'm curious what yall would recommend. Should I just drill two holes just off center of the middle on the bottom of the pipe and call it good? Should I slice larger slats in the flexpvc?

I've got access to tools and time but given how much the 22ft run of pipe cost I'd only like to do this job once :-p

 

[mrsclem]

why not use regular pvc pipe in the bog itself? much cheaper and easier to work with. Just make sure you get regular schedule 40 and not vent pipe.

 

[frogbath]

The main reason is because the bog itself is in a half circle shape and I didn't have a good hidden place the make the transition between flexible and rigid. Using the flex the whole way made it easier for me to hide the pipe as it transitions from the intake bay to the bog (they're right next to each other) and avoid any additional friction from sweeps needed to make a half moon shape for the bog run had I used rigid in there. Besides, I already bought it hehe. I think if I had a longer run or straight shaped bog I would have used rigid. In the end the simplicity of plumbing with one 22ft run of pipe won out.

 

[poconojoe]

I hope the flex PVC is ridgid enough not to get crushed by the weight of the pea gravel. Especially when your drilling holes or cutting slits. That's got to weaken it even more.

I love flex PVC, it's the only hose I will use, but no way would I use it in my bog under the weight of 12" of pea gravel.

I ran my 1-1/2" schedule 40 flex PVC from my pump over the bog/pond wall. The flex PVC is black and I was able to hide most of it with stones.
I made the connection between the schedule 40 flex and schedule 40 ridgid pvc with a Fernco rubber coupling. The Fernco will allow for easy disconnect.

After that, I increased the ridgid PVC to 2".
One leg of my manifold is 10 feet long and the second one is just shy of 10 feet. I cut slits with a sawzall 1/3 through the pipe and 1-1/2" apart. I faced the slits up. Some people face them down.

I used wide sweeping elbows where I could and a "Y" instead of a Tee. But with the force of the pump, I really don't think it matters that much. When I open one of the clean-out stacks, there's a lot of force behind that water. If there are any restrictive bends, i don't think it would matter.
My pump is 3600 GPH.

Come winter, when I turn off the pump, I'll be able to disconnect the Fernco coupling and that will prevent the water from siphoning out of the bog. From what I have read, you want the water to stay in your bog all winter. If it drains, I think it will kill the plants. I guess they will dry out.

Keep us posted on your progress.

 

[Lisak1]

I'm going to second (or third, maybe?) the suggestion to switch to rigid PVC in the bog. I've never seen one built with flex, but I do think it's going to be easier, cheaper and a better tested method to use the rigid. The last thing you want to have to do is dig out that bog once it's planted.

Our transition from flex to rigid is a big ball valve - like @poconojoe , we can shut off the bog to keep the water from draining if we choose to. That came in very handy one year when we had to shut down the pump for a few weeks in the midst of winter. Our bog holds almost 600 gallons, so that's water I was able to save rather than have it flow back to the rain exchange where it would have run out the overflow. Plus like @poconojoe said you don't want your bog to dry out. So even if I did do one long run of flex, I'd add a ball valve to the line... just a though.

But hey... maybe you'll be a trendsetter!

 

[frogbath]

Because the bog is only slightly uphill I didn't think there would be a drain out issue if my pump stopped, but maybe I'm mistaken there? Unless the small run (maybe a foot) upward was enough to start a siphon when it runs back down after shut off, but given the holes throughout I wouldn't expect the suction to be strong enough. This could be a big miscalculation though heh. Guess i should test with some water before I fill it in all the way.

Crush wise I'm less concerned because according to spec sheets flexpvc is approved for below ground use and backfilling. If it's able to be buried below the frost line which around these parts is something crazy like 4ft I think it'll hold up ok to the gravel. However, I think that's probably the reason to go with holes instead of slats so the helix structure on the outside stays mostly intact.

 

[mrsclem]

I did my first bog with holes drilled, it clogged very quickly. Hence the use of slits cut instead.

 

[poconojoe]

The first time I pulled my pump (after adding the bog), I had the (submersible) pump up on the ground to clean the holes in its housing. There was a constant back flow of water out of pump. It was siphoning from the bog and there's not much difference between the height of the pond and bog. Maybe a foot. Just saying....

I can tell you the river stone I used for my bog was quite heavy. When moving it from my truck to the back yard I could only fill my wheelbarrow 1/2 way. It was very unmanageable when filling it close to the top. Again....just saying....

Do what you want, but ridgid PVC is way cheaper than flex and it's...ridgid.

 

[frogbath]

Eeek. Where did yall locate the ball valve? I assume it would be ok to bury it in the gravel as well?

 

[mrsclem]

I use a Fernco coupling on mine. It gets hidden by the plants.

 

[poconojoe]

I have a short piece of ridgid PVC exposed where it connects to the flex PVC(Fernco). I painted it with some green spray paint. Now, especially with all the plants, you can't even see it.

 

[frogbath]

I'm going to do a fill test hopefully tomorrow and see what happens. @poconojoe Was thinking about the siphon issue you talked about and I'm curious whether the holes in your PVC pipe are pointing up towards the gravel or down towards the liner? Maybe it's like the siphon action when the pump shut and the weight of the water? Maybe I should take a video of the aftermath tomorrow :-D

 

[TheFishGuy]

I'm going to do a fill test hopefully tomorrow and see what happens. @poconojoe Was thinking about the siphon issue you talked about and I'm curious whether the holes in your PVC pipe are pointing up towards the gravel or down towards the liner? Maybe it's like the siphon action when the pump shut and the weight of the water? Maybe I should take a video of the aftermath tomorrow :-D

now this is gonna be fun to watch!

I always love to see the fun ( or un fun ) that comes with filling up a pond and seeing if it operates like you want it to! ( it never does trust me )

 

[Lisak1]

Our ball valve is above ground and visible... if you know where to look! It's well camouflaged by plants.

 

[poconojoe]

I'm going to do a fill test hopefully tomorrow and see what happens. @poconojoe Was thinking about the siphon issue you talked about and I'm curious whether the holes in your PVC pipe are pointing up towards the gravel or down towards the liner? Maybe it's like the siphon action when the pump shut and the weight of the water? Maybe I should take a video of the aftermath tomorrow :-D

Here's the deal with mine, yours may act differently.

I didn't drill holes in my pipes, I cut slits and a lot of them. The slits are facing up. If I shut off my pump, pull it out of the water and onto the ground, it has a constant back flow from the siphoning effect.

And think of this...my flex PVC goes over the wall to get to the bog. So, the siphon occurs even with it going up over the wall. Hey, maybe going over the wall helps it since the water is declining? IDK.....

I don't think it would be any different if I had holes (instead of slits) or if I faced them down (instead of up).

I think a sort of vacuum occurs which causes the siphoning.