Building a Pond, Part 2 Waterproofing

I’m taking today off from the yard. Yesterday I poured concrete for our sidewalk since the weatherman assured me there were going to be several at least semi-dry days in a row. I didn’t want to quit until all the concrete I’d purchased was used and I couldn’t be bothered to stop what I was doing long enough to go inside and put some sunscreen on. Now, I’m sorry to say, I have a very nasty sunburn that is keeping me from the yard. So lemonade from lemons and all that, I thought this would be an excellent opportunity to work on my next post about the pond project.

So where were we… oh yes, mud. Lots of mud.

Luckily, I had leveled the edges of the excavation prior to the rain turning the entire pond area into Mudville. I opted for a very simplistic method of accomplishing this: I moved dirt from the higher side of the pond to the lower side until it was mostly level all the way around.
As long as it reaches from one side of the pond to the other, you can use any straight board with a level sitting on top to check level. This works for ponds this size or slightly larger; if you’re doing a much larger pond, leveling will be more technically involved.

Leveling the sides of an organic, freestyle bordered pond is forgiving compared to a formal pond in an exact shape. You still need to level well enough that water doesn’t run out the low side, but minor imperfections can be hidden with rock or plantings.

Perfectly round or square ponds will be noticeably lopsided if the water level is higher on one side than the other. Water will run over the low side and liner will show above the water level on the high side; which makes your pond look silly. Not to mention it can waste a lot of work and expensive materials if you realize that it sucks after the fact and you can’t live with lopsided.

Check for level from every angle, and then check it again before you start moving heavy rocks or mortaring things in place.
Formal ponds may benefit from a brick or concrete block ring set in a light mortar bed around the perimeter of the pond to help it maintain a precise shape and make sure the edge is perfectly level.

Ok, so sides are now level and if you’re me, you’re about ankle deep in mud and not sure whether it feels nice between your toes or just really slimy and gross. It makes a nice SSSSSTHOCK sound when you pull your foot out, which is giggle-inducing to all preschoolers within ear shot. Doubly funny if you lose your sandal to the mud sucking if off your feet. Brownie points if you lose BOTH sandals and nearly get a mud facial trying to rescue them from the bottom of the pond.

I cut my underlayment in half and covered the entire area around the pond and the waterfall, overlapping the underlayment in the middle. An underlayment of some kind under your pond liner is an absolute necessity if you don’t want rocks or sharp roots poking through and destroying all your hard work when you add water.

Water is HEAVY and will cause anything pressing on your liner from underneath to push on it exponentially harder. In the winter, if you leave your pond in place with water in it, this is even more so as the ice pushes up against the walls of the pond as it expands. You need a nice, soft cushion over that hard, unforgiving ground to protect the liner. The clay-type liners are more forgiving in this area, since the clay itself can act as a natural sealant against small punctures. However, a large rip could still destroy even a clay liner, so it’s best to do your prep work regardless of the liner material you choose.
My liner is PVC, because this was cheapest option. EVDM liners are a better choice if you can spend a few extra $; they are stronger (made out of a material similar to car tires) and can tolerate UV rays from the sun better than a PVC liner can.
If you don’t want to fork over the $20 or more for underlayment, a layer of sand and newspaper or cardboard will work instead. Just make sure it’s durable enough that the sharp bits are not going to come through and trash your liner.

After the underlayment is in place, spread your liner out a bit and let the sun warm it up to make it easier to smooth out the wrinkles. A couple of flat rocks on either side of the pond will help hold it in place when you start to add water and can be moved to allow slippage as it fills.

I actually bought two liners for this project, one for the pond and another smaller liner for the waterfall.
The pond liner goes in first, the waterfall liner should overlap it. I had enough for the pond  to run up the waterfall with a bit of slack so that it didn’t stretch too much when I added the large rocks for the waterfall base and then water. Leave plenty of slack at the base of the waterfall liner and let it hang down into the pond. If you’re not doing a waterfall, ignore this entire paragraph. (I probably should have mentioned that BEFORE you read it.)

Liners in place, I filled the pond about ¾ of the way with water, adjusting for slippage as it filled. “Adjust for slippage” is fancy landscaper speak for smoothing out the wrinkles enough that it isn’t tight, but doesn’t look the skin on a Shar-pei puppy either.

The spot where my daughter is sitting in the photo has been dug out to slightly below the rest of the sides in order to build a beach area there later. I put some cement blocks underneath for the time being, just to give us a stable place to climb in and out of the pond and keep the water from spilling out of that area.

You can trim off major excess of liner now if you wish, but don’t trim too close to the edge; you’ll want to leave enough to wrap up around the coping stones (your rocks that border the pond) or tuck under the grass if you prefer the natural look. I saved the really large pieces of leftover liner to put under my big stones and small boulders to guard against tears and punctures.

I can’t stress enough how you should buy a MUCH bigger liner than you need for your project. This will ensure that A) You don’t have a nasty “My liner is too freaking small for this hole” surprise and B) That there is plenty to wrap and use for padding.

At this point, the pond is basically in place, but there is still a lot of ugly black liner showing and a PVC covered pyramid for a waterfall. I’m using a basic drop-in pump with an attached UV filter to move the water. If you’re doing a bio-falls and skimmer, you’ll need to watch their little video or call a plumber, etc. to get that thing installed. The drop in pump was cost effective. Previous years, I actually used one of those fish tank waterfalls disguised under rocks to run my small pond. It worked pretty well and was under $30. The drop-in pump in and filter will run you closer to $100, but it can also handle filtering a much larger pond.

Next, it’s time to do a jigsaw puzzle with a big pile of rock…

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