Losing water is the most common thing pond owners call us about, and a good share of the time there is no leak at all. So before you start pulling rocks apart, confirm you actually have one.
First, rule out evaporation
Every water feature loses water. Evaporation happens whenever molecules escape the surface as vapor, and heat and wind both accelerate it. Splash-out from a waterfall adds to it.
In the Philadelphia area, losing one to three inches a week in summer is normal. That varies by pond. A feature with a lot of surface area, a long stream, or multiple waterfalls will lose noticeably more, both to evaporation and to splatter.
So some loss is expected. The question is whether yours is outside that range. If you are topping off daily, or losing inches in a day rather than a week, keep reading. More on telling the two apart in pond evaporation vs. leak.
Step 1: Turn the pump off and wait
This is the test that narrows everything down, and it costs you nothing but a day.
Unplug the pump. Mark the water level. Let it sit 24 hours without rain. If it is hot and you have fish, drop an aerator in so they still have oxygen with the waterfall off.
After 24 hours, check the mark.
- Water level held, or dropped only slightly. The basin is fine. The leak is in the plumbing or the stream and waterfall. Go to Step 2.
- Water level kept dropping. The leak is in the pond itself. Go to Step 3.
If the pond keeps draining toward a level that puts the fish at risk, move them to a holding tub before it gets there.
Step 2: The leak is in the plumbing or the falls
Start with the plumbing. Inspect every joint and fitting for seepage. This is quick and it is sometimes the whole answer.
Then work the stream and waterfall. Most of the time the cause is not a tear at all. It is plant matter or debris building up behind the weir, raising the water level until it runs over the edge of the liner. A stone settling will do the same thing, and so will liner that has slipped below the water line somewhere along the run.
If it has not rained for a few days, walk the perimeter looking for a wet spot. Wet mulch or soggy gravel where everything else is dry tells you roughly where to look. That one observation saves an enormous amount of hunting.
If you still have not found it, use the technique in Step 3 on the stream bed instead of the basin.
Step 3: The leak is in the pond
Leave the pump off and let the pond keep dropping until it stops on its own. Where it stops is where the leak is, because the water can only fall to the level of the hole.
While it is dropping, check the edges. Look for liner that has sunk down, rocks that have shifted, or a low spot where water is simply running over the top. A low edge is the single most common cause and it is one a homeowner can usually fix.
Once the level holds steady, inspect the liner closely along that exact water line. You are looking for anything from an obvious gash down to a pinprick.
The milk trick. For a fast leak, put milk in a squirt bottle and spray it into the water near the edges at that level. The milk clouds and stays put where the liner is intact. Where there is a hole, you will see it draw toward the opening. This only works on fast leaks. A slow one will not move the milk enough to see.
What causes them
In roughly the order we find them:
- A low edge, or water diverted over the liner by leaves, debris or overgrown plants. Not really a leak at all, and the most common finding.
- Liner that has slipped or settled below the water line.
- A rock that shifted and pulled the liner down with it.
- A tear or puncture in the liner.
- A cracked concrete section.
- A failed skimmer seal, or the skimmer-to-liner connection.
Always check the obvious first. Large rocks that have settled and are weighing the liner down, wet mulch, wet gravel, and the skimmer connection account for a lot of calls.
One repair may not be the whole repair
This is the part people get wrong. A water feature can be leaking in more than one place, and fixing the first one you find does not mean you are done.
After a repair, run the system and watch it for a week. Check the stream, the falls and all the hardware again. We regularly find that where there is one hole in a liner, there are several, because whatever caused the first one usually did not do it in isolation.
When to call somebody
A low edge you can adjust yourself. Move the liner back into position, reset the rock, clear the debris behind the weir.
A tear, a crack, or a failed seal generally needs a professional. Patching a liner underwater is possible and it is not fun, and a patch on a liner that is already brittle tends to buy you a season rather than fix the problem. When we find multiple holes, replacing the liner is usually the honest recommendation over patching six spots.
We do pond leak repair across Bucks, Montgomery, Chester and Delaware Counties, Philadelphia, and South Jersey.
Send us a photo or call 215-880-6811, or get in touch here and we will help you track it down.