Fishpond Repairs | Has My PVC Liner Fishpond Got A Leak?

I received a question from a reader of mine, based in Warsop, England, who was amazed at how much water his pvc liner pond was loosing, when he didn't appear to have a leak anywhere in his fishpond.

For free pond keeping advice sign up for my free weekly newsletter series ...

This is what David wrote ....

"Hi There,

I live in Warsop and have a 200 gallon pvc liner pond that is home to 5 small koi, 3 goldfish and a few parrots feather oxygenator plants. The problem I have is that my pond looses quite a lot of water, almost overnight in some cases. I lost 8 inches of water last Tuesday.

Sometimes when I fill the pond back up the water level remains constant for a couple of days and then disappears again!

I've checked the pond for leaks and can't see anything obvious. Unfortunately I haven't seen the bottom of the pond to see if there is a puncture there. I don't think this is the problem as the guy who installed the pond was doubly careful to make sure that he laid pond underlay down first.

I know that all ponds loose water through evaporation but as you know this summer has been particularly wet with a lot of rain. I read somewhere that evaporation is more of a problem in hot humid weather conditions.

Please can you shed any light on my problem?

Thanks

Dave Milton"

My reply to David was as follows ...

"Hi David,

Has my fishpond got a leak? This is an interesting question and quite a common one believe it or not!

Many older ponds constructed from concrete often suffer from leaks due to small hair line fractures in the porous material. They are often unnoticeable to the human eye. In these circumstances the entire pond will often need to be rendered and sealed with a waterproof sealant. This obviously doesn't apply to you as you have a liner pond but I just thought I would tell you about this anyway.

There are several other factors that may be responsible for your water loss...

Evaporation - This is unlikely to be the major cause of water loss in your case as cooler climates, like the UK don't loose 8 inches of water due to evaporation in a 24 hour span but they do lose water due to evaporation, particularly during hot sunny weather.
Pipe Work Leak - There is a leak somewhere in the hose connecting your pump, UV and filter together. If you are using an external filter which is located above the water level then the cause may be hairline splits in the hose or damaged washers/seals in hose unions. Inspect all pipe work / hose. Look at the soil around the hose to see if it is wet. This is a give away.
Wind - Wind believe it or not is another factor that may often cause a pond to loose water but not 8 inches in one night.
Pump Action - Unfortunately you haven't stated if you have a waterfall or fountain (water feature) as part of your pond set up! If you have then I'm willing to bet that the cause of the water loss is happening because your pond pump is pumping water out of your pond as it powers water to the fountain or waterfall. Somewhere along the route it is escaping from the pond. Stick a liner behind the waterfall or fountain (water feature) you have as this will cause water to run back into the pond.
Leeching - If your pond design incorporates water flowing over quite a large area of rockwork then perhaps water is leeching into the surrounding soil. A liner below the rocks will ensure that any water goes back into the pond. Obviously you need to be careful that the liner isn't punctured.
Splash Out - Taken in isolation over a couple of minutes the water loss onto a patio or lawn from a fountain nozzle, heron scarer or the effects of water escaping from a spray bar of a filter seem extremely minimal. However over a 24 hour period this water loss can add up to quite a few gallons. It is imperative that you use a more conservative fountain head that actually keeps the water in the pond. This is particularly true with a self-contained water feature where the water reservoir is much less limited than in a pond.
Capillary Action - Say your pond design incorporates a boggy area or sunken rockwork then the submerged marginal planted areas or partly submerged rock work is able to act as blotting paper, drawing water out of the pond and into the surrounding area, whether that be soil, cement or a lawn. This problem is fairly common in new ponds where the water loss has not yet been accepted as the norm for the pond. The rate at which the blotting occurs is also in line with the temperature. Water loss is at its highest during the hot summer months. If this is the case then your water loss is not because of a leak but because of the effects of capillary action. Unfortunately there is nothing that can be done about this apart from remove the bog areas and sunken rockwork etc.
Wildlife - Believe it or not if your pond attracts birds and other wild life who use it as a convenient place to cool off or take a quick shower then this will also contribute to possible water loss. Although not generally too much water loss it will however play a contributing factor. Some pond keepers will use wire mesh or pond netting to keep the birds at bay.
High Water Levels - Leaks associated with high water-table levels underneath the pond liner, have been known. This lifts the pond liner, allowing the pond water to spill over the edge of the pond. A aesthetically pleasing solution is to weigh down some water lilies, or water plants and place them in the middle of the pond, thus sinking the liner.

Try this ...

Fill up your pond and shut down the Pond Pump overnight. See if you are still loosing water.

If you are then you have a leak in your PVC pond lining. If you don't then it is the pump that is causing the water loss. In this case check the tubing between the pump and the fountain or waterfall. You may have a loose connection or a tear in the hose.

What I would also advise you to do is to replace any old connectors with new ones. For a minimal cost it will help to eliminate one possible water loss culprit.

As we all know water can get almost anywhere, particularly where we don't want it to at times. A slight misalignment can be enough to steer the water off it's intended course.

Unfortunately the simple question of "Has my fishpond got a leak?" is not always that easy to answer. It is simply a case of having to eliminate possible causes until you manage to identify the actual cause.

Hope this solves your problem ...

ps please be aware of the following when filling your pond back up:

Tap water contains chlorine and in some instances chloramine and other heavy metals. This in high enough dosages can be poisonous. Buy a Chlorine/Chloramine Water Treatment from your local gardening centre or aquarium stockist. Add the specified dosage to your pond.

Oh yes one other thing make sure you don't leave your pond pump switched off for longer than need be otherwise ammonia levels will rise. This can harm your fish."

Use Innotec Adheseal Sealant In The UK For Fishpond Repairs

By the way a great product recommended by a newsletter subscriber of mine by the name of Gary is Innotec Adheseal Sealant if you are looking to completely seal any hose joints from leaks. Although expensive and can be messy, it does the job of sealing annoying leaks on hose joints and also minor repairs. I would recommend the 290ml tube as it can be used in a sealant gun. Due to the consistency of the sealant I found it difficult to squeeze out of the smaller 50ml metal tube and it split (very messy).

For those of you who are interested in knowing about why you shouldn't switch your pond pump off, apart from in instances such as that above check out Why It Is Important That Your Fish Pond Water Pump Runs Continuously 24/7 ...