Design review: Raised Pond with Rain Curtain

[Waleed K]

Hey folks,

Thank you so much to the folks on the forum for the guidance I've received so far!

I'm preparing to undertake a revamp of the water feature in the backyard we have and am looking to expand it to some 700 gallons. But before spending thousands of dollars and a couple of hundred hours on the project, I thought I would run my design past the wise minds on this forum.

I've actually put together a Google doc on the project where you can directly add comments here. So if you'd prefer to review it in Google docs, you can. I've replicated that document here, and would love to get your thoughts on:

- Is this totally crazy?
- Will the suggested support structure for the pond be sufficient?
- Is the approach to filtration correct?
- Any thoughts on ways to keep the cost down?

Raised Bed Pond Design with Rain Curtain

The goal of this project is to take an existing originally pondless rain curtain and turn it into a 700 gallon pond. This is to make it deeper so that the water temperature doesn’t significantly fluctuate, and also to make it resistant to attacks from predators (raccoons, herons). And to accommodate more fish -- mostly goldfish. Perhaps one or two koi (after making an agreement with a friend to take them on once they get to 2 feet).

The original water feature looked something like this:

With the central pool being about 11 inches deep. The goal of this project is to add a raised component taking the total depth to 29 inches, but also expanding its footprint (such that its front-to-back size is increased from about 40 inches to about 120 inches).

Raised component construction


The planned construction technique is to use raised bed planters from Home Depot to make a stack 3 high:

Then hammer rebar through the center holes to anchor them into the ground.

Then use 2x6 wood to go into the slots, but also to vertically stack them to make a solid 4.5 inch thick wall (which should be able to take the 800 gallon weight).

So that the entire frame looks like this:

Then put a 2x10 end cap on it to make it look nice (see first picture). Plan is simply to screw it onto the 2x6 foundation.

Lining
The plan is to put a pond underlay and a 45mm EPDM pond liner, and stick it to the top of the 2x6 boards, then put the 2x10 endcaps on top of the liner.

Filtration & Waterflow

The plan is to use a Tetrapond Skimmer as the primary point of entry into the filtration system. A pump then sucks water with debris removed and then drives a pressurized filter. The output from the filter is split via valve in two streams: one to the rain curtain, and one to an output in the pond, designed to generate a current so that leaves etc end up in the skimmer.

Budget

 

[sissy]

I like it or can I say love it .

 

[Meyer Jordan]

How are you securing the 2 x 6s to each other?

 

[Tula]

What a unique pond

 

[sissy]

The blocks are made to hold the 2x6's .I have used them before but in the middle you may have to screw a board to them to keep them from bowing out from the weight of the water .The planter blocks have a hole in the center to put rebar in .I only did mine 2 high at my sisters and 18 feet long filled with dirt for a raised bed for her .How do you plan on locking the planter blocks to the water feature part .Not sure you have to lock it to them but not sure either .Those planter blocks I got for 1.98 on sale during the 4th of july last year

 

[Waleed K]

Thanks for the feedback! Keep it coming -- sincerely appreciate it. Still not quite sure about the filtering plan.

@Meyer Jordan I was relying on gravity for vertical attachment (relying on the rebar inserted into the planters), and I was going to put galvanized wood screws to hold them together horizontally.

@sissy I was planning to have them 3 deep (so effectively 4.5" thick wood to prevent bowing). I wasn't planning on attaching to the water feature -- just mounting them right next to it.

But I was planning on putting rebar through each stack (3 feet rebar, so 18" above ground, 18" below).

One thing I've been thinking about is how do I suck stuff up from the bottom of the pond. I considered a bottom drain, but then I'd need a settlement chamber which would cut into the space. I also considered a debris handling pump, but I couldn't work out what to do with its output -- if I connected it to a pressurized filter, it would just jam up the pressurized filter.

 

[Meyer Jordan]

One thing I've been thinking about is how do I suck stuff up from the bottom of the pond. I considered a bottom drain

Old reliable wet/dry vac.

 

[Mmathis]

I like the idea! But a couple of things to consider is evaporation will be greater, and I think that 700 gals is too small for koi....perfect for a few nice goldfish. And what about putting the shower closer to one end instead of in the middle -- that would give the fish more "open" space, and you could add plants like a water lily (they don't like a lot of water movement). Really is a pretty and unique design and can't wait to see pics when you're done!

 

[Jhn]

Cool idea for a pond.

My suggestion is to pocket screw each vertical stack of 2x6's to each other rather than relying on gravity, so they boards act as one solid board. Otherwise the boards may tend to warp differently overtime as they dry out. As others have said the boards may bow even stacked 3 thick depends on the span between those blocks.

Also,the 2"x10" top cap to finish, if possible would reduce it to a 2"x8". With nothing under the one side of the top cap it may cup with a 2"x10". Would depend on the width of the vertical columns for the rain curtain. Also, to prevent cupping wrong way of top cap boards be sure to crown the board.

Lastly, I would 45 the 4 corners of the top cap (better finished lookon 90 degree corners)and pocket screw along the underside of the joint.

A pocket jig can be bought from home depot.

 

[sissy]

use a swimming pool net to clean the bottom ,I have used one for years

 

[Waleed K]

@Jhn Sincerely grateful for your woodworking advice. I'll look at the pocket jig approach for the vertical support too.

The rain curtain's width is 9.25" (ie. the same width as 2 x 10), so I really wanted to have it match. Since the planter blocks are 8" across, I figured it was still OK to have a 2" overhang; but you might be right. When you say crown the board, you mean place it so the natural bend in the board along the 10" face is facing upwards.

Will also look at a 45 degree mitre for the corners.

Thank you for the great suggestions!

 

[Jhn]

@Jhn Sincerely grateful for your woodworking advice. I'll look at the pocket jig approach for the vertical support too.

The rain curtain's width is 9.25" (ie. the same width as 2 x 10), so I really wanted to have it match. Since the planter blocks are 8" across, I figured it was still OK to have a 2" overhang; but you might be right. When you say crown the board, you mean place it so the natural bend in the board along the 10" face is facing upwards.

Will also look at a 45 degree mitre for the corners.

Thank you for the great suggestions!

No problem....

yes you crown the board by looking at the end grain on the board. Should be in a sort of U shape, lay it down so the U is facing down.
Sometimes it doesn't matter what you do the board will still warp, but these things will help prevent it.

10" board is fine it may not warp, just be particular about which boards you get, since it is what you will be looking at when done. I was just thinking if it looked right aesthetically the 2"x8" would have less chance of warping.

Like I said that is a really cool idea for a pond, never even occurred to me to try a rain curtain in a pond.