Leakinjg pond.

[william jones]

I live in North Cornwall, SW England and dug a pond in my garden maybe 18 years ago and have thoroughly enjoyed it since then. It has a butyl liner which has always been trouble free but has recently showed signs of leaking. I then found and repaired the leak but after this it appeared to continue to leak although at a reduced rate so kept looking for a leak which I'm not sure exists any longer. I then hit on the idea of blowing air into area behind the liner in several places using a car tyre pump and looking for bubbles and didn't see any. I did this with reducing amounts of water in the pond (about 8" minimum). So maybe there is no leak and I just put it down to evaporation.
So was this idea a bad one because expert opinion predicts that that it wouldn't work anyway? If so how do you work out what water loss there will be due to evaporation using maths?

Thanks for any help.

 

[barryian]

I live in North Cornwall, SW England and dug a pond in my garden maybe 18 years ago and have thoroughly enjoyed it since then. It has a butyl liner which has always been trouble free but has recently showed signs of leaking. I then found and repaired the leak but after this it appeared to continue to leak although at a reduced rate so kept looking for a leak which I'm not sure exists any longer. I then hit on the idea of blowing air into area behind the liner in several places using a car tyre pump and looking for bubbles and didn't see any. I did this with reducing amounts of water in the pond (about 8" minimum). So maybe there is no leak and I just put it down to evaporation.
So was this idea a bad one because expert opinion predicts that that it wouldn't work anyway? If so how do you work out what water loss there will be due to evaporation using maths?

Thanks for any help.

You didn't have major evaporation before so why would you have it now, right? 18 years is a long time. Are there areas that seem brittle? Possibly after winter, you're losing water from your waterfall? How low does it go? Does it stop at a certain point as the level it stops at would be the level of the leak! Do you have a skimmer or main drain as those would be the first 2 places to check. There is a color dye that you can use in areas you can reach and the dye would be sucked in, even in a fairly slow leak.

 

[Kevin Koloff]

Agreed probably aged. My epdm liner life expectancy is around 25 years. I did have a substantial leak last year, and was very worried. Turned out the pump line drain valve was leaking, and with the waterfall pump running, it was pumping water out.

 

[Meyer Jordan]

If so how do you work out what water loss there will be due to evaporation using maths?

There is an mathematical equation for determining evaporation rate. It is call the Penman Equation. For a pondkeeper it is really of no use because one needs to know such values as vapor pressure, air densities, etc. just to get a figure that has probably changed while the equation was being worked out.
Simple rule of thumb is: If the rate of water loss is fairly consistent, then it is a leak; if the rate of water loss varies and is rarely more than 1/4 inch per day, it is evaporation.
Once a pondkeeper experiences dealing with a leak, a certain level of paranoia creeps in and the slightest change in the water level imparts a state of panic.

 

[CometKeith]

Hmmm. I thought I had a liner leak last year for about two months because I was always losing water. I thought it might have been connected to an incident where one of my limestone waterfall rocks fell in the pond which could have made a hole in the liner. I did everything possible to check the liner including draining a lot of water and doing a thorough liner inspection. As a last resort before I changed it I either changed or recut the ends of all my hoses to and from my filters to make really good seals even though I couldn't see anything leaking. The leak went away and has been fine since. It saved me a lot of work and probably saved a few of my fish that would have undergone a traumatic time from a liner change in the middle of the summer.

 

[william jones]

Thanks to all who replied with very helpful comments but I still don't know whether I've got a leak or not. What I would really like to know is whether the test of blowing air behind the liner is any good. After all this is the classic and well tried way of finding punctures and other air leaks. It involves a portable 12 volt compressor designed to inflate car tyres and doing this tells me that there is no leak but is it reliable or not. I can't believe others have not tried it so how did they get on?
I fully accept that those who pointed out that the liner was an old one are perfectly correct but I really don't want to change it if there is no leak and the air test says that there isn't. But is it reliable?
Thanks for the evaporation maths but measuring all these values is beyond my resources.
Anyway thanks again.

 

[MitchM]

...What I would really like to know is whether the test of blowing air behind the liner is any good. ...

The simple answer is no, that won't work.

.

 

[barryian]

Thanks to all who replied with very helpful comments but I still don't know whether I've got a leak or not. What I would really like to know is whether the test of blowing air behind the liner is any good. After all this is the classic and well tried way of finding punctures and other air leaks. It involves a portable 12 volt compressor designed to inflate car tyres and doing this tells me that there is no leak but is it reliable or not. I can't believe others have not tried it so how did they get on?
I fully accept that those who pointed out that the liner was an old one are perfectly correct but I really don't want to change it if there is no leak and the air test says that there isn't. But is it reliable?
Thanks for the evaporation maths but measuring all these values is beyond my resources.
Anyway thanks again.

Most definitely, wouldn't blow the air! Wouldn't work very well at all. I have a 2000 gallon pond and evaporation is so insignificant that if I had a leak, I'd know it. Meyer said a 1/4 inch/ day wouldn't be a leak. Maybe, maybe not but if the line at the weir on my savio were down 1" every 4 days, I'd check my water fall to see if it were running back. If it was good, I'd know I had a leak. I rarely ever add water as rainfall usually balances it out. In North Cornwall, your temps are quite cooler than here in the summer and your rainfall should balance out your pond. Exactly how much water are you losing in how long a period?

 

[Meyer Jordan]

Most definitely, wouldn't blow the air! Wouldn't work very well at all. I have a 2000 gallon pond and evaporation is so insignificant that if I had a leak, I'd know it. Meyer said a 1/4 inch/ day wouldn't be a leak. Maybe, maybe not but if the line at the weir on my savio were down 1" every 4 days, I'd check my water fall to see if it were running back. If it was good, I'd know I had a leak. I rarely ever add water as rainfall usually balances it out. In North Cornwall, your temps are quite cooler than here in the summer and your rainfall should balance out your pond. Exactly how much water are you losing in how long a period?

It really depends on the configuration of your pond and the total surface area of exposed water. The pond and stream that I had was a total of 700 sq.ft. exposed water surface (stream, wetlands and pond). Because water loss manifested itself only in the main pond basin, it was normal for me to lose 1" to 2" of water daily. Absolutely no leaks...all evaporation and evapotranspiraton.

 

[barryian]

It really depends on the configuration of your pond and the total surface area of exposed water. The pond and stream that I had was a total of 700 sq.ft. exposed water surface (stream, wetlands and pond). Because water loss manifested itself only in the main pond basin, it was normal for me to lose 1" to 2" of water daily. Absolutely no leaks...all evaporation and evapotranspiraton.

Wow - That's outrageous! I have a 17' x 35' oval pool with water temps of 85-89F. When I had a leak prior to rebuilding it 3 years ago, I was losing 1/2" a day. That was a leak. If I lost 1-2" of anything a day, I'd swear it was a leak or swear at the leak. That is an amount of amazing evaporation... Many variable as temps, wind and breezes, surface area ...

 

[Meyer Jordan]

Wow - That's outrageous! I have a 17' x 35' oval pool with water temps of 85-89F. When I had a leak prior to rebuilding it 3 years ago, I was losing 1/2" a day. That was a leak. If I lost 1-2" of anything a day, I'd swear it was a leak or swear at the leak. That is an amount of amazing evaporation... Many variable as temps, wind and breezes, surface area ...

Look at my overall square footage again and add in my location. Normal evaporation rates.

 

[Meyer Jordan]

Keep in mind that these are annual amounts, includes all days rainy, overcast, sunny, etc. Sunny and partly cloudy days will run a much higher rate than the daily average realized from this map, as will Mid-Summer days.

 

[william jones]

Thanks to all who replied with very helpful comments but I still don't know whether I've got a leak or not. What I would really like to know is whether the test of blowing air behind the liner is any good. After all this is the classic and well tried way of finding punctures and other air leaks. It involves a portable 12 volt compressor designed to inflate car tyres and doing this tells me that there is no leak but is it reliable or not. I can't believe others have not tried it so how did they get on?
I fully accept that those who pointed out that the liner was an old one are perfectly correct but I really don't want to change it if there is no leak and the air test says that there isn't. But is it reliable?
Thanks for the evaporation maths but measuring all these values is beyond my resources.
Anyway thanks again.

The simple answer is no, that won't work.

.

Hello Mitch M,
Thanks for your reply but your simple answer is a bit too simple so I have to ask the question why won't it work?

 

[MitchM]

Because you will never be able to create a seal between the pond liner and the substrate so that sufficient air pressure will be created to have the air forced out through the liner and into the water column.
Give it a try and you'll see what I mean.

.

 

[barryian]

View attachment 90053
Keep in mind that these are annual amounts, includes all days rainy, overcast, sunny, etc. Sunny and partly cloudy days will run a much higher rate than the daily average realized from this map, as will Mid-Summer days.

Yes, your rates are 50% and more higher than mine!