Hi!


We are installing a toilet, since we have to use cast iron pipes so we has to use cast iron flange.
The plumber installed and seems the flange is attached with cast iron pipe but not screwed to floor/sub-floor.
I see flange installation in internet are all not cast iron but all are attached to floor/sub-floor.

Our cast iron flange is not attached to sub-floor. Is this how suppose to be installed?

Some times the flanges cannot be screwed down if there is no backing beneath the floorboard, but you need to check if the flange is solid enough to set your toilet. Take hold of the flange and pull up with your hand, if it moves easily then you need to address the problem before setting toilet.if you don't have a crawlspace or a ceiling beneath sometimes you don't have a choice but to cut a section of floor out to strapdown the drainline , and put in some wood backing so you can screw down the flange for a solid installation. Good luck on this matter.

Mitsu, who told you that you have to use a cast flange if you have cast pipes? Twist-N-Set® Cast Iron Replacement Closet Flange :: Oatey.com If there isn't enough sub floor under your toilet to screw the flange down you should be addressing that issue. The flange makes the air tight seal between toilet and sewer line but is is not designed to carry the weight of a toilet and person, the floor carries that weight. Is thjis a licensed plumber or a handyman?

He is a handy man, unfortunately since non licensed plumber.
It is newly constructed bathroom so sub floor was also newly installed. However, our plan is to have floor tiled. Does the flange suppose to be installed over the tile or screw down to sub floor (which covered by Ditra.)? Anyhow, the iron flange have 4 screws to tighten to the iron pipe. So he opened a such a big hole to the sub floor and can not be screw down. Also, the flange is about 1 inch higher than the sub floor for expecting the tile to be installed under the flange.

Exactly... the flange will sit down over the tile. Then will drill holes through the tile to secure the flange.

Home supply stores sell an anchor kit for this (see pic.). Here, you set the flange after tile is installed, then drill holes in tile with the 1/4" mason bit that comes in the kit. Then set the anchors into hole and screw the flange down tight.

Let us know if you need more... Mark

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Mitsu, your handy man is a bit unhandy when it comes to making holes. Is there easy access to this sewer pipe from below like in a basement? The flange can sit with its surface flush with the tile surface or it can be sitting on the tile, that is your range where a single wax ring should seal.