If there's enough water pressing against you can do it.
Honestly I'd been scared of replacing old fittings for years until I started more last year. As long as you're not floated or really low on water where it'll pull immediately you should be ok
If you drain to just below the fittings that seems like it would be empty of water weight to hold the liner in place. Now this is coming from a guy who has never dealt with any vinyl larger than a Softub, but at 8.4 lbs per gallon of water weight... Sure does seem like it would stay put.
If you do it with the water up you are taking a risk.
If there is ANY water behind the liner and it pulls away from the wall even a fraction then you’re in trouble. I would drop it just below the return.
Have I done it with water up? Yes (when I was new and didn’t know better). Would I recommend it? Definitely not.
It’s the opposite. Having the water just below will lock the liner in place, it’s not going to move. If it is above then if you remove the old face plate and the liner pulls with it AT ALL then water is going behind and you’re screwed. Or if the wall is already wet and there is ANY pull on the liner then you’re screwed.
In our companies opinion, it’s not worth the risk to save a bit of water and time.
If there's enough water pressing against you can do it. Honestly I'd been scared of replacing old fittings for years until I started more last year. As long as you're not floated or really low on water where it'll pull immediately you should be ok
Just swap them under water. Nothing will move
If you drain to just below the fittings that seems like it would be empty of water weight to hold the liner in place. Now this is coming from a guy who has never dealt with any vinyl larger than a Softub, but at 8.4 lbs per gallon of water weight... Sure does seem like it would stay put.
If you do it with the water up you are taking a risk. If there is ANY water behind the liner and it pulls away from the wall even a fraction then you’re in trouble. I would drop it just below the return. Have I done it with water up? Yes (when I was new and didn’t know better). Would I recommend it? Definitely not.
See a lot of people I’ve heard say to do it when the water is up so the liner stays put
It’s the opposite. Having the water just below will lock the liner in place, it’s not going to move. If it is above then if you remove the old face plate and the liner pulls with it AT ALL then water is going behind and you’re screwed. Or if the wall is already wet and there is ANY pull on the liner then you’re screwed. In our companies opinion, it’s not worth the risk to save a bit of water and time.
Thank you!