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How can I tell if my tub is steel or cast iron?

Posted by LARemodel (My Page) on
Fri, Jun 20, 14 at 12:07

I like my current tub, but remodeling the bathroom will likely mean pulling out the old tub, which is "tiled in." I know that it is not fiberglass / acrylic because a magnet will stick to it.

How can I tell whether the existing tub is steel with porcelain or cast iron with porcelain? I tried the "thud" test, but still can't tell which it is.

Will I be disappointed if I switch to a fiberglass / acrylic tub?

The current tub is 66" long. I have been thinking about getting a 72" long tub and re-arranging the layout. It is awkward to have to step into the tub to open or close the window - which looks into my neighbor's house.

Attached is a "before" picture. A designer helped me choose the tile color - which I've always regretted. A 2nd designer helped me to choose the wallpaper (now peeling) to soften the color of the tiles.

This post was edited by LARemodel on Mon, Oct 13, 14 at 15:51


Follow-Up Postings:

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RE: How can I tell if my tub is steel or cast iron?

Found this on another site:

1) Remove the overflow cover and popup lever from the head end of the tub and look at the edge of the hole. You should see black cast iron or bright steel. Also, if you remove the overflow cover, the material between it and the plumbing will be about 1/4 " thick if it is cast iron. 1/16" if it is steel.

2) Tap the tub with your fingernail, and if it has a light, tinny sound (tak, tak, tak), it's steel; if it sounds more solid, resonant or bell-like, it's probably cast iron. Most steel tubs would have the same feel that kicking an older car might be imagined to be, where as cast iron would feel much more solid, like kicking a large rock.

3) If you can pick it up without giving yourself a hernia it is not cast iron.

Love the last one. LOL


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RE: How can I tell if my tub is steel or cast iron?

Do you know what brand it is? Kohler never made steel tubs, that I am aware of, for example.


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RE: How can I tell if my tub is steel or cast iron?

I was going to recommend what la cochina posted.

Thickness of material is the easiest way to tell. You can sometimes flex the wall of a steel tub with simple pressure.


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RE: How can I tell if my tub is steel or cast iron?

Thanks. I'm still uncertain.

It took me a while to get brave enough to unscrew the overflow cover - the edge looks black, not shiny at all. There's no "pop-up" lever - there's a toe-tap to close the drain. The finger-nail tap test sounds neither "tinny" nor "bell-like" to me. There's no brand name on the tub. I would need to be superhuman to even consider trying to pick up a tub that is tiled in.

The tub has been in place since the house was built in 1987. It still looks "new." The water stays warm for at least 20 minutes (I've never actually timed it).

When I looked at acrylic / fiberglass tubs in showrooms recently, I noticed that some were scratched, and I've read that they are intended to last only about 20 years.


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RE: How can I tell if my tub is steel or cast iron?

Do you need to operate the window?

I think if it were me, and the tub were in great shape (and remains in good shape after the tile is removed--no scratches), then I'd keep that tub. It looks great. It doesn't take up a lot of room (isn't one of those mini pools that call themselves a tub) and it is already larger/longer than standard sized. 72" tub is really long--bordering on minipool again.

If the main complaint with function is that you can't operate the window without stepping into the tub, and the window is facing a neighbor, why would you want to operate the window? Would it be more effective to replace the window or window treatments than the tub?


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RE: How can I tell if my tub is steel or cast iron?

I think the tub probably is cast iron. When I tap on the slope of the back, I hear more of a bell sound. The tiling on the apron may be muffling any sound when I tap on the sides of the tub. On the drain cover, it says "Made in Taiwan," and it looks like cast iron tubs may have been imported from Taiwan in the 80's.

The main incentive for the bathroom remodel is a serious leakage problem with the shower pan in the stall shower. A secondary reason is that the entire layout has never been ideal. Third reason is that all the small tile and grout is a pain to clean. Fourth reason is the decor (tile) is dated.

I don't know if it's possible or cost-effective to remove the tiling around the tub without damaging it. It would be challenging to design a new bathroom around the old tub with the existing tile.

I need to operate the window; it is the only source of ventilation in the bathroom. Changing the layout would provide easier access to the window. I've thought of several alternatives - add a fan, add another window, change the window configuration (awning-type window), or find a window treatment that provides privacy without sacrificing ventilation.

While the exterior length of the tub is 66", the interior length is 44". The depth is 15". I'm 5'1" and this size works for me, but probably not for the average-size adult.

My teenage son likes to take baths. He's a foot taller than me and has long legs. I took him with me to try out some longer tubs - even some of the 72" tubs are too short for him, depending on the slope of the sides.

Given that I'm accustomed to a cast iron tub, will I be disappointed if I replace it with a new acrylic / fiberglass tub? There are some other types of materials, such as Victoria & Albert tubs and WetStyle tubs; I'm thinking about looking at these.


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RE: How can I tell if my tub is steel or cast iron?

If you are going to be remodeling, I'd replace the tub and tile surround. You've already mentioned that the tub is a bit small for a taller person and to me, it looks a bit dated. It would also be a good opportunity to replace the bath fixtures as they also look a bit worn.

We replaced our cast iron with an acrylic air tub. Our cast iron was in great condition, but no longer liked the color. The reason we went with acrylic was: 1) We were doing the work ourselves and the cast iron tub was difficult enough to remove. Seriously doubted that we could have installed a new one by ourselves without injury or damage; and 2) We wanted an air tub. Can't tell you how durable it is yet because we are still finishing up the remodeling and have yet to use it.

We did replace our aluminum window above the tub. We opted for a heavily frosted awning window which I love. It's easy to open and it blocks the view of our neighbor's house while still letting in lots of light. We also have a good bathroom fan which I would recommend as well. During the winter months, you do want to have good ventilation without having to open a window.

Lots of decisions to make, but if you are remodeling a portion of your bathroom, you might as well do the rest of the tub area being that there are already issues with it that you are unhappy with.


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