Pond liner size

[max384]

After this harsh winter which wreaked havoc on my 300-400 gallon pond, I've decided to build a new larger pond. It's roughly an 8' x 12' oval pond. Here is a quick illustration of the pond with some dimensions:

I've put my rough dimensions into a few pond liner calculators and I've been told to use a 20' x 20' liner. However, using a cloth tape measure running along the surface of my pond which is now dug, I come up with 14' along the widest part of the width and 12' along the widest part of the length. This is without measuring for overlap. So, shouldn't a 15' x 20' liner work, and even provide over a foot of overlap on all sides? I'm wondering if the liner calculators use a cylindrical shape for determining liner size. Thus, my sloping sides would cause an overestimation of the amount needed? I know the bigger size would be a safer bet, but we're talking a $100 difference between the 15x20 and the 20x20... and right now money is an issue for me. I wouldn't even be upgrading the pond if it weren't for needing to spend money to fix the damages from the winter on my current pond. I'm going to be putting in a bottom drain and increasing the size of the biofilter. I could skimp on either of these two in order to get the bigger liner, but I'd rather not if possible. I could also go with the thinner liner instead of the 45 mil EPDM. My current pond was made with some thin 20 mil (if I'm remembering correctly) liner and I've had no problems with it... But I'd rather go with the thicker liner this time around.

I was actually about to pull the trigger on the 15' x 20' after doing my measurements, but I'm just checking to see that there isn't anything obvious I'm overlooking. I just don't want to pay for excess that I won't use anyhow just to be safe.

Thanks.

 

[JBtheExplorer]

If I'm calculating right,

12' length + 3' depth, plus another 3' for the liner to come back up, plus 2' (one foot of overlap on both sides) is 20'

8' max width plus 6' (for depth again) plus 2' (for overlap again) is 16'

You'll need a 20x20

 

[talal101]

If I'm calculating right,

12' max length + 6' (6' = 3 feet of liner going down and 3 back up) plus 2' total of overlap is 20'

8' max width plus 6' (for depth)plus 2' (for overlap) is 16'

Am I doing my math wrong here, but what about the extra liner for the cliff inside the pond, wouldn't it be:

1(initial drop)+3(drop to the deepest part)+3+1+8+2 (overlap) = 18 or even 2+3+3+2+2 (overlap) which would equal a 20 foot liner for the thinner part and an even longer liner for the longer part.


wait never mind....I was calculating an extra 3 feet under the already there 1 foot cliff. JB's math is spot on. I would always go with 45mil and I would always get the 20X20...extra is better, less is not

 

[JBtheExplorer]

what about the extra liner for the cliff inside the pond

What you want to do is take the deepest part of the pond (3ft) and thats how much extra liner its going to take to get to that depth from ground level, then times it by two because the liner has to come back up. Here's a graphic I did to help show it. each bar represents one foot

 

[sissy]

I gave my size to dr foster and smith and they made sure i had the right size when i ordered mine in March .I had a little extra that I needed but in the end I just went higher which made it a little deeper and had extra for my little water fall pond plus enough to sit my stock tank inside the liner .I told the how I did my stock tank and how long and length was perfect .Sides a little extra never hurts .Better to big than to small

 

[sissy]

to give you an idea my pond is 8 ft wide by 4 ft deep and it is just around 16 ft and actually liner that i got was just about a foot wider and just about a foot longer than i ordered.I measured it spread out on the lawn my liner was supposed to be 20 by 25 turned out it was 21 by 26 .That is why I decided to go deeper .I told them around 3 1/2 feet deep .Remember folds on an oval or round take a little more work .I only had corner folds.I did have to add a little liner over the other liner up by the filter tank since the pond was a little longer than 16 ft .Forgot to stop digging or maybe tape measure was off .Hubby told me the digger was a little off also .So i have plenty of excuses .

 

[talal101]

What you want to do is take the deepest part of the pond (3ft) and thats how much extra liner its going to take to get to that depth from ground level, then times it by two because the liner has to come back up. Here's a graphic I did to help show it. each bar represents one foot

View attachment 68905

Yeah I totally forgot about the liner that already counts towards the depth....my bad. I caught my mistake as I was editing to clarify where I was getting the measurements.

 

[sissy]

..I used a big piece of my old liner that was good for my waterfall pond section and my tank .No biggy since water was only going down into the pond.Right under the rocks is where I started the old liner .Uyp at the top where the waterfall is is where I went less deep since i had to be able to get in the pond

 

[JBtheExplorer]

@max384 another option would be to go slightly smaller. I'm using a 20x15 for my 11x6 pond, though I'm also going 3.5 at my deepest spot. its similar to your layout. I did 3.5 deep on the left, 2 deep on the right, and a 1ft shelf for plants around the edge

 

[talal101]

@max384 another option would be to go slightly smaller. I'm using a 20x15 for my 11x6 pond, though I'm also going 3.5 at my deepest spot. its similar to your layout. I did 3.5 deep on the left, 2 deep on the right, and a 1ft shelf for plants around the edge
View attachment 68918

Am I the only one who has fun making diagrams of ponds?

 

[sissy]

coloring book for ponders

 

[max384]

Thanks for all the help guys! I decided to play it safe and just buy the bigger 20x20 liner... I won't starve because of it I guess! But since I was buying the liner, I decided to dig it a little bit bigger!! So now it's about 11x12' and 40" at the deepest.

It looks far from impressive in the picture, but here is the "finished" hole:

Good thing I had a couple helpers to give me a hand!

 

[sissy]

hey you have helpers .See bigger liner bigger pond

 

[addy1]

nice hole and nice helper

 

[Big Lou]

20'x20', you will not regret it. Good luck and have fun!