Building a rain exchange - here's a tip

[Lisak1]

Here's a very niche piece of advice: for anyone who's thinking of building a rain exchange/negative edge pond, here's a tip for your rock in the rain exchange - LESS IS MORE. We have fought with slow drainage in the rain exchange almost since the beginning and have tried various things to keep the water flowing. Lots of raking and cleaning and what not - we even removed all the pea gravel and replaced it with larger stone...same issue. Drained great for a few weeks and then slow slow slow. Last year we bought a small power washer which helped a lot, but this year even after power washing we had about a week of good water flow before things started to slow down. I remember asking Brian Helfrich when we saw his rain exchange set up how he kept the water flowing - "oh the guys come and dig it out for me every spring and replace it with new gravel!" Ah... OK.

The biggest issue for us is our pond overflow is inside the rain exchange "pit" so if the water gets too high in there, it drains to the storm sewer - which is by design, but meant to happen only in the case of a heavy rain - not as a daily occurance because the gravel won't allow the water to drain. But problem number 2 is it just doesn't look great. The water gets kind of murky and the rocks get caked with slimy stuff... just not real pretty to look at.

Long story short, this spring I took a serious look at the situation and decided to start shoveling out the rock. I took six-5 gallon buckets of rock out of the pit, leaving just enough to cover the softball sized boulders that are on top of the aquablocks. Low and BEHOLD - it worked. The water flow is excellent and best of all we aren't losing any water down the overflow. The pond level has stayed 100% consistent for weeks now. AND the whole situation looks so much better. We have a small amount of pooling water in the rain exchange which is perfect - not a whole pit full of water that is slowing draining out of the pond!

So my advice to you - if you're filling a pit with gravel and hoping water will drain through it consistently - USE LESS GRAVEL!

Now I just have to figure out what to do with all this extra river rock...

 

[Tula]

Makes total sense and a good tip for others

 

[GBBUDD]

Lisak1 said:
Here's a very niche piece of advice: for anyone who's thinking of building a rain exchange/negative edge pond, here's a tip for your rock in the rain exchange - LESS IS MORE. We have fought with slow drainage in the rain exchange almost since the beginning and have tried various things to keep the water flowing. Lots of raking and cleaning and what not - we even removed all the pea gravel and replaced it with larger stone...same issue. Drained great for a few weeks and then slow slow slow. Last year we bought a small power washer which helped a lot, but this year even after power washing we had about a week of good water flow before things started to slow down. I remember asking Brian Helfrich when we saw his rain exchange set up how he kept the water flowing - "oh the guys come and dig it out for me every spring and replace it with new gravel!" Ah... OK.

The biggest issue for us is our pond overflow is inside the rain exchange "pit" so if the water gets too high in there, it drains to the storm sewer - which is by design, but meant to happen only in the case of a heavy rain - not as a daily occurance because the gravel won't allow the water to drain. But problem number 2 is it just doesn't look great. The water gets kind of murky and the rocks get caked with slimy stuff... just not real pretty to look at.

Long story short, this spring I took a serious look at the situation and decided to start shoveling out the rock. I took six-5 gallon buckets of rock out of the pit, leaving just enough to cover the softball sized boulders that are on top of the aquablocks. Low and BEHOLD - it worked. The water flow is excellent and best of all we aren't losing any water down the overflow. The pond level has stayed 100% consistent for weeks now. AND the whole situation looks so much better. We have a small amount of pooling water in the rain exchange which is perfect - not a whole pit full of water that is slowing draining out of the pond!

So my advice to you - if you're filling a pit with gravel and hoping water will drain through it consistently - USE LESS GRAVEL!

Now I just have to figure out what to do with all this extra river rock...


As you may know I have similar but with the usual a bit of a twist.
Over the negative edge the water drops into a smallish pool like 8x6x2.5 that area is where I place the net to catch large debris it's there most of the time.as I can't see it from the patio where we usualy hand out.
This is hardly fool proof and I was still getting debris in the overflow but mine goes to a 3000 gallon cistern and not the storm drain . I use to have a diy fabric basket but that became clogged and had to make an other over and over and it usualy clogged so fast that.i wasn't even sure how much it was doing. So i seem to be on a video kick so heres my take on the same.
@Lisak1 and her issues mentio ed here were known from this site and added to the solutions I made to my pond.

 

[GBBUDD]

Now I just have to figure out what to do with all this extra river rock...

Makes for great ground cover around trees in the garden but it needs to be played out just dropping it will look like it was just droped.

 

[j.w]

I use bigger river rock here and there for decor in my garden beds. Most are bigger than baseball size but I have a few that are that size and I just place them wherever they look good. I don't have a ton tho.

 

[Lisak1]

I did use a good amount for the usual "frog catching spots" around the pond. My grandkids love to hunt the frogs and they have a few spots that are primo, so nothing will grow there anyway - might as well give them a spot to stand that's not going to be wet, muddy, or slippery.

I love the net solution - I use my net any time we do any major clean up to catch the big debris, but mine is front and center in the pond view, so it doesn't live there. I do think about building a custom "net" or basket that would fit up and under the waterfall rock... but then don't I just have a skimmer?

 

[GBBUDD]

I did use a good amount for the usual "frog catching spots" around the pond. My grandkids love to hunt the frogs and they have a few spots that are primo, so nothing will grow there anyway - might as well give them a spot to stand that's not going to be wet, muddy, or slippery.

I love the net solution - I use my net any time we do any major clean up to catch the big debris, but mine is front and center in the pond view, so it doesn't live there. I do think about building a custom "net" or basket that would fit up and under the waterfall rock... but then don't I just have a skimmer?

I believe your much like Brian's set up where water comes over the negative edge and drains through the gravel. I was never a fan of this ss it traps debris but no way to get it out without a lot of work.
I'd seriously consider digging out the rock and in hope you have about 3 inches.
I would then place a blue matala mat ( fine) on your aquablocks then place a black matala mat (course) ontop of the blue mainly for color but also much easier to clean. And when you see any backing g up wash them or just beat them upside down and your back up and running.

 

[Lisak1]

We modeled ours precisely after Brians - which is why we used pea gravel and layers of underlayment over the aquablox and between the larger and smaller gravel - big big mistake, as we both found out. You know what clogs faster than pea gravel? Underlayment. We spent the first two years cutting that out and getting rid of the pea gravel.

Brian actually had a grate installed one year when we toured his pond - much like you'd find at the opening to a garage with a down hill driveway to catch the rain run off. The waterfall spilled directly into the grate. He said that worked but he didn't care for it aesthetically. Plus any kind of gravel in those grates defeats the purpose. (And yes - we've toured Brian's pond every chance we got.)

I've thought of your filter mat idea - it may still come into play at some point. My only concern is the amount of biofilm that tends to grow on the filter pads - you know the gooey, slimy stuff? I worry that would just create another clogging issue.

Our set up now is working well - first time I can actually say that. It's aquablox, topped by softball sized boulders, topped with river rock. It's flowing great and looks clean. Live and learn is the name of the game I guess!

 

[GBBUDD]

I've thought of your filter mat idea - it may still come into play at some point. My only concern is the amount of biofilm that tends to grow on the filter pads - you know the gooey, slimy stuff? I worry that would just create another clogging issue.

I have been running the green matala in the cistern 2 years now. It has only ever show signs of clogging once. And lift it out hit it on the ground upside down and your good to go again. Now I did use the blue in the baki shower and that did clog and back up. But again pull it out and hit on the ground upside down a couple times and it's ready to go.

The green only catches big stuff leaf remnants moss food etc . Black too course to be all you use imo