Stock Tank Filter and Liner Replacement

If it seems like I do something new with our stock tank pool every year, so far that's true! last year we redid the cover, and the inner liner sprung a leak at the end of last summer. So this spring, we relined the pool, replaced the filter, and integrated filtration into the side of the pool! No more vacuum loops, just way less finicky filtration.

I used some additional equipment as well, and I definitely will be using it in the fall so we can fully empty the pool for winter. Most folks in our Northern states flip their tanks when emptied, but I’m not in that group. The liner is designed for above ground pools that can’t be flipped, and the tank can withstand anything.

Emptying the Pool

​With a liner, this is trickier than just opening the drain, even if the liner leaks. So, I got a submersible dirty water pump that could handle getting the majority of the water out without trouble. I did have some difficulty with it sucking the liner into the pump, so we put a metal grate in to hold the liner out of the suction. It was an effective solution! But I’ll likely use something a little less pokey in the fall to make sure the liner stays intact.

The rest of the water was pulled out with our shop vac; we just had to make sure it was the one with the sponge filter wet situations.  After we cut the liner out and removed it, we repeated the process. There was a significant amount of water that came through.
Then we got a few inches of rain, and did it again!

Reorganizing the Filter

For the first four years, we used a vacuum loop system for filtration: with a pair of j-pipes and long sink extensions, we were running a hose into the filter to prime it and using the filter pump to maintain suction in and out of the pool. Filtration worked well, but it left pipes in the water that needed to be monitored for suction loss.  This year, I elected to swap it for a more standard above-ground system.

This process was fairly straightforward, and a lot like plumbing a tub drain with a few extra layers of sealant.

1. I cut two 2 3/4" holes in the side of the stock tank. I did need to pick up a new hole saw, as my largest two options were 2 1/2"... and 5". Getting the size closet to the diameter outside the threads was critical in getting the holes sealed without worry. The smaller the gap, the easier the install.
2. I then got the liner mostly adjusted -more on that later- so I had one section lined up well with the holes in the tank. I cut an X in the liner to correspond with each hole.
3. I rolled a bead of plumber’s putty in my hands long enough to wrap around the threads on the threaded fitting for the filter, then wrapped it around the fittings and pinched it into a circle. I then pushed it through the X in the liner from the inside out.
4. Then I tightened the fitting with the O-ring against the tank as tightly as possible, squeezing out excess putty as I went. This provided a fairly tight seal against the side of the pool.
5. Just to be secure, I slathered the edges of the fittings on both the inside and outside of the tank with silicone to ensure a well sealed system, and I let that dry for 24 hours.

Setting the Liner

Getting the liner in required getting it laid in the pool as flat as possible and draping the sides along the outside of the pool. Getting it lined up and in place with nothing to help hold it in place was near impossible, so I added a few inches of water to the pool to help secure it as I wiggled out the wrinkles on the bottom.

Then, with the filter fully installed, I filled the pool and trimmed the liner, adding the same pipe insulation I've added in years past to give it a soft edge.  At this point, waterproof tape is needed to secure the liner to the pool. Since liners are 4’ tall instead of 2’, it is possible to not trim the liner to fit the height, but if it gets trimmed, tape is essential to prevent water from getting in between the liner and the tank.

Full disclosure: we didn’t tape the liner at first! So we got to do this whole thing twice this summer. Luckily, we could still use the stock tank in between liners too. Relining twice is still worth it to get to play with these kids outside. Who knows, maybe we’ll add a heater and extend the season one of these years.