YShahar
Enthusiastic duct-tape engineer
OK folks, the time has come to talk of many things...
Specifically of pond liners and liner protection.
First, the soil situation: as I mentioned in my pond build post, I'm digging into something that is almost pure limestone, with very little actual soil in it. Think sharp angular rocks pointing in all directions. So I'm going to need more than the usual cushioning underneath my liner.
My first thought was to put in a 10 cm deep layer of sand. However, that won't help cushion the sides. In addition, if I buy in bulk, the 500 kilo bag(s) of sand would have to be dropped into my neighbor's front yard, and from there moved, one bucket at a time, down two flights of stairs to our front yard, around the house and then down another flight of stairs to our back garden. It's doable, but would add a huge amount of extra work, especially as I'll be doing it almost entirely on my own.
So here's what I thought to do, and you can tell me whether this sounds workable:
I've got 20 big concrete paving slabs measuring 45 x 45 cm by 5 cm deep. I'm thinking of covering the bottom of the deepest area beneath the liner with these slabs, as well as any part of the pond that will see foot traffic (shelves leading from the entry beach area down into the deep end). On top of the slabs, I'll add underlayment. For areas that won't have concrete slabs under the liner, I'll add extra underlayment, plus odds and ends (old carpet, styrofoam, etc.) that I have lying around.
What do folks think: overkill or not?
Now to the liner itself... I've priced Pondgard liner at local aquatics suppliers, as well as EPDM roofing material. Here is what I found out:
Pondgard 89 shekels / square meter (about $28 per square meter). So for a 7 X 10 meter sheet (70 square meters) the cost would be 6,230 shekels, or $1930.
Roofing liner from a building supply company: 870 shekels (about $279) for a roll measuring 10 x 20 meters (200 square meters). By comparison, the same size in Pondgard would cost 17,800 shekels (more than 20 times as expensive as the roofing membrane).
Now I'm aware that the pros and cons of Pondgard vs. roofing EPDM have been discussed on the forums. And of course, the guys at the aquatics stores swear up and down that regular EPDM is practically a doomsday weapon against fish. On the other hand, I talked to a guy who uses EPDM for roofing, and has also built some large fish ponds for a local park. "EPDM is EPDM!" he said. "It's all exactly the same stuff!"
So it was time to do an experiment. I went over to my favorite building supplier and bought a roll of 10cm x 200cm EPDM of the sort that would be used in sealing roofs. According to their website, this is the same stuff as used in the larger sheets, only cut much narrower (10 x 200 cm rolls is the smallest they have). I then went out and bought a cheap glass aquarium and 5 goldfish. I set up the aquarium with good filtration and some water plants and let the fish acclimatize for a month. I then moved two of the goldfish to a separate spare aquarium to use as a control group. I then cut a sheet of 20 cm worth of EPDM off the roll, rinsed it (giving it no more rinsing than I'd be able to do with a full-size liner out in the yard), and dropped it into the more established aquarium.
Results so far: all the fish are healthy and happy, and the ones in the EPDM-contaminated aquarium seem to spend as much time nosing around the stuff as they do nosing around the gravel at the bottom. So my inclination is to go with the roofing membrane (at 20 times cheaper and much wider rolls). Since it's sold only in 20 meter rolls, if I buy a 10 meter wide roll, I'll have plenty left over for a later bog filter and other side projects.
So folks, anyone see anything wrong with my reasoning here?
Go ahead. I can take it! ;-)
Specifically of pond liners and liner protection.
First, the soil situation: as I mentioned in my pond build post, I'm digging into something that is almost pure limestone, with very little actual soil in it. Think sharp angular rocks pointing in all directions. So I'm going to need more than the usual cushioning underneath my liner.
My first thought was to put in a 10 cm deep layer of sand. However, that won't help cushion the sides. In addition, if I buy in bulk, the 500 kilo bag(s) of sand would have to be dropped into my neighbor's front yard, and from there moved, one bucket at a time, down two flights of stairs to our front yard, around the house and then down another flight of stairs to our back garden. It's doable, but would add a huge amount of extra work, especially as I'll be doing it almost entirely on my own.
So here's what I thought to do, and you can tell me whether this sounds workable:
I've got 20 big concrete paving slabs measuring 45 x 45 cm by 5 cm deep. I'm thinking of covering the bottom of the deepest area beneath the liner with these slabs, as well as any part of the pond that will see foot traffic (shelves leading from the entry beach area down into the deep end). On top of the slabs, I'll add underlayment. For areas that won't have concrete slabs under the liner, I'll add extra underlayment, plus odds and ends (old carpet, styrofoam, etc.) that I have lying around.
What do folks think: overkill or not?
Now to the liner itself... I've priced Pondgard liner at local aquatics suppliers, as well as EPDM roofing material. Here is what I found out:
Pondgard 89 shekels / square meter (about $28 per square meter). So for a 7 X 10 meter sheet (70 square meters) the cost would be 6,230 shekels, or $1930.
Roofing liner from a building supply company: 870 shekels (about $279) for a roll measuring 10 x 20 meters (200 square meters). By comparison, the same size in Pondgard would cost 17,800 shekels (more than 20 times as expensive as the roofing membrane).
Now I'm aware that the pros and cons of Pondgard vs. roofing EPDM have been discussed on the forums. And of course, the guys at the aquatics stores swear up and down that regular EPDM is practically a doomsday weapon against fish. On the other hand, I talked to a guy who uses EPDM for roofing, and has also built some large fish ponds for a local park. "EPDM is EPDM!" he said. "It's all exactly the same stuff!"
So it was time to do an experiment. I went over to my favorite building supplier and bought a roll of 10cm x 200cm EPDM of the sort that would be used in sealing roofs. According to their website, this is the same stuff as used in the larger sheets, only cut much narrower (10 x 200 cm rolls is the smallest they have). I then went out and bought a cheap glass aquarium and 5 goldfish. I set up the aquarium with good filtration and some water plants and let the fish acclimatize for a month. I then moved two of the goldfish to a separate spare aquarium to use as a control group. I then cut a sheet of 20 cm worth of EPDM off the roll, rinsed it (giving it no more rinsing than I'd be able to do with a full-size liner out in the yard), and dropped it into the more established aquarium.
Results so far: all the fish are healthy and happy, and the ones in the EPDM-contaminated aquarium seem to spend as much time nosing around the stuff as they do nosing around the gravel at the bottom. So my inclination is to go with the roofing membrane (at 20 times cheaper and much wider rolls). Since it's sold only in 20 meter rolls, if I buy a 10 meter wide roll, I'll have plenty left over for a later bog filter and other side projects.
So folks, anyone see anything wrong with my reasoning here?
Go ahead. I can take it! ;-)
