Back To The Family Handyman
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Beginning the Project
Digging the hole
After marking the pond
and berm with spray paint, throw the excavated dirt into the berm perimeter.
You’ll be able to sculpture the berm’s final shape and size as you excavate. We
suggest digging the hole only 1 ft. larger than the pond walls to minimize
digging and the amount of gravel fill needed against the pond walls. But
in loose soils, the hole walls may begin caving in and you may have to dig a
larger hole. Don’t let the hole sit for days on end before you set up the pond
walls because the sides will eventually collapse, especially if it rains. (Ask
me how I know this!)
Choose the highest grade point to determine digging depth and dig down 32 in. from that point. That way the 36-in. high pond lip will still be several inches above grade after you add the gravel footing. Use any type of clean gravel or sand for the 4-in. deep pond footing and base.
The finer the gravel, the easier it is to level. Just roughly level the gravel with a steel rake, then follow the simple method we show using stakes and a screed board to level the gravel footings directly under the walls. If your soil is sand, only dig a 38-in. deep hole, skip the gravel and use the sand for the footings, liner base and backfill.
Treated wood walls
We recommend ground
contact (.40 retention) treated wood for the wall, footings and deck framing.
If foundation-grade lumber (.60 retention) is available at the lumberyard,
choose it for all the below-grade materials and the pond structure will last
virtually forever. Use double hot-dipped galvanized nails for fastening the
framing but screw the plywood to the inside with deck screws. Nails could work
their way out and puncture the liner. Note that each layer of pond wall plates
overlaps the one below it. That’s to spread the
load over a larger area, help tie everything together and even out slight
inconsistencies in heights.
Installing the liner and the liner pad
The liner pad protects
the rubber liner from being punctured by sharp stones and rough framing
surfaces. Before you install the liner pad, carefully inspect the walls and
take care of protruding fastener heads, splinters or sharp stones that could
work their way through and puncture the waterproof pond liner. It’s easiest to
install the liner pad by cutting a separate piece slightly larger than the
bottom and then cutting separate pieces for the sides. They hang over the pond
lip and drape over the walls (stapled to the outside), overlapping the bottom
liner. You can cut up the liner pad as much as you need to as long as you
overlap the pieces. Keep pleats and folds to a minimum and the pond liner will
fit better.
We spread out the pond liner on the grass and roughly cut it to size with a utility knife before dragging it over the pond and pushing it into position. It’s easy to catch it on sharp objects and puncture it, so be careful. Slip out of your shoes and work in your socks when standing on top of the liner and fitting it against the walls. The key to a good-looking job is neat corner pleats, so spend some time on careful folds. After filling the pond with water, tack the liner around the outside with roofing nails and cut off the excess.
Customizing the skimmer and biofilter
The skimmer and
biofilter need customizing
to work in your particular pond. First of all, you’ll have to measure the width
of the skimmer inlet, including the skimmer flange.
Custom-size the wall opening to fit your skimmer opening. We recommend making
it about 4 in. wider than the skimmer flange to accommodate folding the
liner through the wall and
screwing it to the skimmer basket. The opening height isn’t too important,
since the basket sits outside the wall. After the liner is clamped to the
skimmer, fill the space between the wall opening and the liner with sand to
support the liner against the pressure of the water.
TIP: Dig the skimmer and biofilter basket holes deeper than needed and fine-tune the bottom heights by adding gravel. It’s easier to level than soil.
The pumps that come with the kits are generally powerful enough to drive a sizable waterfall over the lip on the biofilter. To throttle down the water flow to the trickle needed for the sluice, buy a separate PVC valve to fit in the hose leading from the skimmer to the biofilter. But simply replacing the kit pump with a smaller one may make more sense because it’ll cost less to run. Buy a pump that lifts water 6 ft. (it’ll say on the back of the pump box) and a smaller hose that fits the pump outlet and is long enough to reach from the skimmer to the biofilter. Drill holes above the water lines of both the skimmer and the biofilter baskets for threading the hose through and connecting the new pump. The water line in the biofilter must run all the way to the bottom of the biofilter so the water can flow up through the filtration system. Keep the larger pump for draining the pond when necessary.
Our biofilter came with a separate lip that functions as a spillway or built-in waterfall. We discarded the lip and cut a replacement spillway out of decking and then cut a slot to receive the sluice. The replacement spillway is then caulked and screwed into the biofilter spillway opening and the sluice is sealed in the slot with silicone caulk.
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