FlexPVC Bog - Drilling vs Cutting

[Jhn]

Agree with @poconojoe your line from the pump to the bog will back siphon and empty the bog until the line sucks air from somewhere to break it ie the bottom of the bog. It doesn’t matter how high your line is running just the fact that it is going up higher will do it.

You can put a check valve in the line or right above your pump to prevent this or somewhere in your pipe run drill a small hole in it, like right before where it goes into the gravel for the bog. This way when it is pumping water through it the little bit of water that comes out the hole won’t drain the pond it will just squirt on to the gravel at the top of the bog. However once the power is shut off to the pump that hole will suck air and break the siphon.

 

[frogbath]

Ah, thanks @Jhn, I remember hearing about that hole drilling trick on an older thread when I first started researching this. Totally forgot about it! I was considering a check valve too but it's probably just better to switch to rigid like seemingly everyone is suggesting and do a ball valve. I was kinda worried about the check valve fowling up with algae over time.

 

[Lisak1]

Ours is the same - the main line goes vertical up a 2.5 feet wall, then horizontal for 6 feet, then over the edge of the bog and down to the bottom another four feet. When the pump goes off, the bog will empty back to the pump. We have a check valve ahead of the pump to keep the bog from emptying when the pump is connected, but if you have to disconnect the plumbing for any reason the bog will empty. Hence the ball valve.

And maybe in some cases it wouldn't matter if the bog flowed back to the pump, but if that pump were in the pond, you'd be emptying potentially dirty water back into the pond. Or in my case, back to the rain exchange and I'll lose whatever amount of water the rain exchange can't contain to the overflow. In a bigger bog, that can be a significant amount of good pond water lost.

 

[Lisak1]

Ah we were cross posting!

I know in our case we felt it was easier to add the safeguards and not need them than to not have them and regret it later.

Should we now talk about ball valves and what kind to get?

 

[poconojoe]

Won't a ball valve get damaged by freezing?

 

[mrsclem]

I use them on all my filters, never had one get damaged. I have had a gate valve freeze and break.

 

[Lisak1]

We have four on our plumbing - never had a problem with freezing. Ours have had two issues - they got realllllly hard to turn and the plastic handles dried out from exposure and cracked when we had to hammer them to get them to turn. So we replaced them with a much better quality valve with a removable handle and used Vaseline on them before we installed them to keep them turning easily.

 

[brokensword]

I would suggest maybe placing a T between the valve and bog, with screw cap (so you can induce that air break and stop backflow) for this reason; with a check valve, I do believe water can still remain in the line. I'd rather not have any pipes above water level, full of water, when winter and freezing temps hit. There will be water at pond height and at bog water height, but if you have air between, the possibility of cracking a pipe won't be there. With mine, I've used 4" corrugated drain pipe (slits every 2", facing up), to which my 1-1/2" pump supply is attached. I placed large rocks on both sides and over top of this pipe, then covered with another layer of large (4-6") rock followed by a layer of 2" cobbles then pea gravel. My supply comes off a T with the water fall so when I shut the waterfall down, air is induced and I don't get back flow. Each line/sub line has a valve to regulate as I see fit.

 

[Lisak1]

Good call @brokensword - this is why we've always disconnected the plumbing ahead of the check valve when we had to turn off the pump in winter time - the check valve will keep water in the line.

 

[frogbath]

I posted a video in the construction thread that shows the bog setup. I ended up drilling pretty large holes in the flexpvc and facing them downward and out to the side, say at 7 oclock and 5 oclock if you imagined the pipe as a clock face. The pipe was still rigid so I decided to try it out. I did end up needing to put a check valve in cause like everyone said it totally backflowed.

Interestingly when I killed the pump it didn't back flow anymore but if there was enough water in the pond it was flowing UP and into the bog. I suspect this is due to the check valve's placement allowing a siphon to start in the other direction. Kind of unexpected. I'll keep yall posted over the next few days. Hopefully I don't have to rebuild my bog too soon.

 

[addy1]

- they got realllllly hard to turn and the plastic handles dried out from exposure and cracked

I use only these still working great many years later. Gave up on the red handle ones.

https://www.lowes.com/pd/AMERICAN-VALVE-PVC-SCH-40-2-in-Socket-PVC-Ball-Valve/1000339525

 

[Lisak1]

You were the one who clued me in on those @addy1 - replaced all of ours with these and haven't had a bit of trouble since. Our handles are still red, but they are removable so I can store them indoors away from the constant sun, heat, cold, etc.

 

[poconojoe]

I would suggest maybe placing a T between the valve and bog, with screw cap (so you can induce that air break and stop backflow) for this reason; with a check valve, I do believe water can still remain in the line. I'd rather not have any pipes above water level, full of water, when winter and freezing temps hit. There will be water at pond height and at bog water height, but if you have air between, the possibility of cracking a pipe won't be there. With mine, I've used 4" corrugated drain pipe (slits every 2", facing up), to which my 1-1/2" pump supply is attached. I placed large rocks on both sides and over top of this pipe, then covered with another layer of large (4-6") rock followed by a layer of 2" cobbles then pea gravel. My supply comes off a T with the water fall so when I shut the waterfall down, air is induced and I don't get back flow. Each line/sub line has a valve to regulate as I see fit.

That's a great idea! Adding a tee with a screw in cap would do the trick. Just unscrew the cap when shutting down the pump.

 

[addy1]

You were the one who clued me in on those @addy1 - replaced all of ours with these and haven't had a bit of trouble since. Our handles are still red, but they are removable so I can store them indoors away from the constant sun, heat, cold, etc.

All the ones here have white handles. They all stay outside, some get taken apart as part of my pump removal for the winter. They work great, those red handle ones are a night mare.

 

[Lisak1]

Agreed - and every single one should either come pre-lubricated or come with instructions to lubricate. It makes a WORLD of difference.

We have one more in the basement I need to get switched out - it's the one we use to switch the sump pump water from the pond to the storm sewer. When we get a ton of rain we have to switch it over and it's always a chore. It's not falling apart like the outside ones, but it's a dickens to turn.