Clean it as you have before.
Bury the silicone, unopened, 20 ft. deep in a land fill.
If your tube is not castiron, fill about 1/2 full of water and apply Polyseamseal.
The tool is your dampened finger, it remains flexible, mold resistant and is paintable.
http://www.polyseamseal.com/

I like GE Kitchen/Bath caulk. Have never used the Polyseam product, but it sounds like basically the same as the GE stuff.

Your tub was probably not properly secured to the wall studs when it was installed or the studs have rotted. Perhaps you can repair it from the other side of the wall.

Where the joint is too large use a foam backer rod before applying the sealant.

When silicone sealant is removed even the slightest residue will prevent additional silicone from adhering. The surfaces must be cleaned with mineral spirits.

Polyseamseal has been a great adhesive sealant for over 30 years but the original product is sometimes not flexible enough for use at showers and tubs. However, Henkel now makes 9 different kinds of sealants under the brand name of Polyseamseal so you must be careful which you choose.

Four of the Polyseamseal products are recommended for showers & tubs:

- "Ever Bright Silicone Sealant", a 100% silicone sealant with some antimicrobial agents added especially for tub & shower use.

- "Speed Seal", a fast-drying 100% silicone sealant.

- "Tub & Tile Adhesive Caulk", a water-based Polyvinyl Acetate adhesive similar to the original Polyseamseal product.

- "Tub & Tile Ultra Sealant", a water-based acrylic sealant with silicone added for increased flexibility and durability.

In my experience, acrylic sealants (even those with silicone added) perform poorly in wet areas. PVA sealants adhere the best but are not always flexible enough for tubs.

No sealant comes close to the flexibility of 100% silicone but it must be installed properly because it does not adhere to substrates as well as other kinds of sealants.

For a sealant to expand and contract properly it should have an hour-glass shape because that maximizes the adherence at the edges while minimizing the resistance to stretching and compressing at the center. The best way to achieve this shape is to use a foam backer rod behind the sealant and properly tool the front to be concave. Often the tile backer board and tile are not properly installed at a tub so there is no space for a backer rod and the sealant is forced to completely fill the gap thereby reducing the life of the sealant. Silicone sealant will help but any sealant will fail faster in such a condition.

Thanks for the info and tips. I will try mineral spirits (hope it's available in a tiny can!). I did try using foam backer rod, but since I only had a pretty wide-diameter piece, I broke pieces off from that. Maybe I should get smaller ones. Does it come as thin as 1/8"? ANd how will I stuff it in there? I would only need a few inches of it.
I still need someone to tell me the best compromise for how big to cut the tip of the tube (Hope I dont' have to buy several tubes!).

I never used acrylic on this tub, only 100% silicone.

I believe the construction firm I used was competent and properly installed the tub, backer board, etc. based on architect and engineer specs. I can't get into the wall from the other side (well, not easily), because it is an outside stuccoed wall. I doubt there is rot, since it's only a few years old, and the problem hasn't worsened, just persisted.

Since my tub IS cast iron, is it best to skip the tub-filling step, or can/should I still go ahead and do that?

Thanks!

Yes you can, and while 1/4" is a little wide, with this product you can apply it in multiple layers successfully.
I've used the ALL PURPOSE for over 20 years, because I am not trade specific.
You'll find the ease of tooling a relief.

Polyseamseal "All Purpose Adhesive Caulk" is the same as Polyseamseal "Tub and Tile Adhesive Caulk" without the extra mildewcide. The manufacturer does not recommended it for showers and tubs and specifically warns not to use it under shower door tracks. Both of these products are essentially adhesives and adhere very well to non-porous surfaces but only The Tub & Tile Adhesive Caulk should be exposed to water repeatedly.

The manufacturer warns that if the joint exceeds 1/4" x 1/4", a backing material should be used. Of course, ideally the joint should be deeper than it is high so that a foam backer rod can be larger than the joint height so that it will be compressed when installed and form a firm curved surface to form the sealant. Sealan should never be built up in layers to entirely fill an oversized joint.

Here is a link that might be useful: Polyseamseal

I looked at the link, and it looks like Polyseamseal is NOT a silicone product. Right? My understanding is that once a silicone is used in an area, other caulks will never adhere. Am I missing something?

Also- every caulking instruction I have ever looked at specifies cleaning well before caulking with ALCOHOL (denatured or rubbing), never mineral spirits. Will m.s really do a better job, and be safe for the surface?

If you read the information on the Polyseamseal site you will find that Polyseamseal is not just one product but several including 100% silicone, Acrylic, Acrylic with silicone added, and Polyvinyl Acetate which is the original adhesive based sealant.

The site recommends using mineral spirits for immediate clean up of their (uncured) silicone products (others recommend rubbing or isopropyl alcohol) and to use a knife blade and an abrasive cleaner to remove old silicone.

Since abrasive cleaners can damage surfaces you might want to try a commercial silicone remover like linked below. You can Google "silicone remover" for other products.

Here is a link that might be useful: silicone remover

"Sealan should never be built up in layers to entirely fill an oversized joint."

Sorry, no sale.
I've been using it for over 20yrs. in sinks, lavs, tubs and showers, with no warranty callbacks, just over 60 regular customers and their referrals.

All my work is from referals, I do not advertise.

I'm not selling anything. Perhaps you should contact ASTM and advise them on changing their standards for installation of sealants.

Its always interesting to me that some contributors on these boards site organizations who have done studies and have developed standards of use for products and applications, without listing a specific document, chapter and/or paragraph for review, all of which are readily available.
The obvious implication being that any entrepreneurial action you may use would not be practical and destine for failure, as if you consume food beyond its published expiration date will surely sicken you.
Also missing from these references is that their predominant inclusion is in government contracts for the specific purpose of standardization of performance.
There are other contributors who post from practical experience. The experience of tried and true methods that serve them and/or their clients, past or present, with products and applications designed to ensure longevity
of practical use and performance.

Well, getting back to my tub...

I just removed the old caulk (well, most of it; I'll tackle the final scrub later), and I noticed something that I'd forgotten since the last time doing this - not only is the gap variable in height (in some places, barely thicker than a few sheets of paper!), but there are also some sections where grout comes all the way down to the tub surface. Should I try to chip that stuff out? It looks like the last time I just applied the caulk (a very thin layer) right over it. Not sure if that's a problem.

I also did not find any backer rod thinner than 3/8-inch, which I already have. The clerk suggested I might try using screen spline. Has anyone ever done this? Any reason it wouldn't work?
If I do decide to do layers, just to fill some space, should I let them dry in between? I'm not actually sure how I'd get it in there in the areas that are small in height (way too small for the nozzle) but big in depth.

Thanks to ALL of you for your advice.

There should be no mortar in the bottom joint or touching the tub.

It's hard to understand how tile could be installed above a tub with an uneven joint. Perhaps you need to replace the bottom row with tiles cut to the proper size. How close does the tile backerboard come to the tub rim and what is it made of? There should be enough room for a 3/8" backer rod but if the joint is less than 1/4" you can omit it.

I'm not sure how the joint ended up so unequal. It's not like there is a jagged, uneven, bottom line - it's straight(ish), but I guess it must slope a bit or something.

Yes, I know there shouldn't be grout/mortar along the bottom joint, but from what I hear and read, it's a common shortcut (later, when we had our kitchen done, I made sure to insist that they leave the Corian/tile joint open for caulking). I'm also not sure why it's only there at some tiles, and not others (making it trickier to use backer rod, or a substitute). I sure hope I don't have to re-do the bottom row - what a pain! I will have to check the photos I took (luckily) to see how close the backerboard comes to the tub rim. What will the answer tell me?

I think last time I sliced lengths of 3/8" backer rod and stuffed it into some of the joints, but I'd prefer to find something a little more "elegant" this time. It definitely won't fit in whole.

I don't think I've ever heard the term "elegant" associated with backer rod or caulking before.

Yes, let the coats dry to the point where the product is stable, then reapply. Allowing a short drying time will allow the adhesion to occur and keep the tooling of the successive coat from pulling.

I have a similar problem with caulking areas being wider in areas. I think my tub has also settled in one corner since every time we shower, water stands in a corner and has to be dried up with a towel. I have caulked 3 times already this year and it is cracking again. Who would be able to level the tub if needed--a plumber or contractor??

I have the same problem please let me know if you find an answer

ruzzella, 10 year old post, you are better off starting a new thread and explain you entire issue including what you have done to this point as most people will not respond to a decade old post....................

im having the same issue described. We just bought this house with a recently renovated bathroom and the tub is pulling away from the floor and wall. We are hoping it is just a settling thing and not a major structural issue. Someone is coming to take a look but would love ant thoughts!