Oftentimes (sorry, I did type that with my pinkie in the air…) you don’t have access to the floor beneath your shower in order to install your drain. Not usually a problem unless your drain pipe beneath the floor is hanging in the wind! Okay, not hanging in the wind, but not absolutely sturdy either.

It’s difficult to get a good seal when installing your drain if your drain pipe isn’t solid. It pushes down as you try to push the drain onto it. That doesn’t work. So get yourself some string. Or wire. Or anything else you can wrap around your drain pipe beneath the floor and up through the hole for the drain.

DO NOT use one of your wife’s scarves! Not that I’ve, umm, done that…

Wrap the string around the p-trapThe photos I have are of a floor I replaced completely, but the same can be done through just the 4 1/2″ opening you need for the kerdi drain. Yes, it also works for regular drains.

First get your string wrapped around a spot on the pipe where it won’t slip off, because that will cause you to invent a whole new vocabulary of cuss words. Trust me on that. I normally wrap it around the opposing elbow of the p-trap. See the S-shaped pipe? That’s the P-trap. Obviously named by an alphabetically challenged plumber…

Tape the string to the top of the pipeNext, if you are replacing the floor, tape the top of your string inside the top of the pipe. Doesn’t really do any good if you can’t reach it when you need it.




Pull the string through the hole in the floorOnce the floor is in grab your string and pull it back out of the way of your drain.





Install adhesive to drain and pipeInstall the proper adhesive onto both your drain and pipe (and primer, if using pvc). Make sure your string doesn’t slip down into the hole!





Push drain while pulling stringFit the drain and pipe together. Press and twist down on the drain while simultaneously (yup, pinkie in the air…) pulling up on the string to force the pipe against the drain.

Now you can either sit there and hold the string while the adhesive cures, or you can pound a nail into your substrate to wrap it around while it cures – your choice. Depends on how much time you have and how close your beer Pepsi is.

Once it cures you can remove the string and you’ll have a good seal between your drain and the pipe without going completely insane! (Well, any more than you already are, anyway…)

Hey Plumbers! I know what the ideal situation is with the drain, p-trap, brackets, etc. This is for people who do not have the ideal situation, and can’t get below the floor to make it ideal. So if you’re gonna give me shit about it at least try to be funny. :D MMK?Thanks.

{ 47 comments… add one }

Leave a Comment

  • Bill

    Hi Roger,
    Great stuff!
    My tiled bathroom floor is in great condition except the almond grout is dirtier than we like. Do you know of a special product to clean the grout.
    Thanks very much.
    Stay safe in this Covid time.

    • Roger

      Hi Bill,

      Try oxygen bleach (OxyClean). Mix it up, pour it on there, let it soak for a bit, scrub, then rinse REALLY well. That normally removes most dirt stains in lighter grout.

  • John

    any way to fix this? I cut the 4.5″ hile and attached drain fitting to subfloor. I am several steps farther along now.

    • John

      sorry, did not realize my other post went through. I removed screws and can lift drain fitting and pipe up. OK to block it with 3/4″ plywood pieces and mud it in place?

      • Roger


  • Jerry

    Hi Roger. I just purchased your Creating a Traditionally Waterproofed Shower and the Tile Tips. I read the shower book and understand it. It appears to be a very detailed and easy step by step process. I look forward to starting my shower! I also, just started reading the tile tips and learned so much in just a few short pages. It will definitely help me in all my tiling jobs. I then read your article concerning the waterproof methods. Now, I have a question.

    Would it be a bad thing to do both the traditional and then top it off with RedGard? Or, is that overkill? I know the RedGard is expensive, but it sounds like it would be cheap insurance. Also, could this be used on the floor too?

    And, then I started reading some of your articles and it appears that you put tile to tile in the corners and caulk it rather than leaving a grout joint and grouting it. Is it better to place tile to tile and caulk, rather than leaving a spacer and caulking it rather than the grout.

    Thank you so much for the information and your time in answering these questions. I look forward to your answers and to building my shower.

    • Roger

      Hi Jerry,

      Yes, you want one or the other, never both. You don’t want your substrate trapped between two impervious layers, any moisture trapped there will promote mold growth. You don’t want it on the floor if you have a traditional membrane either – same reason. I know it sounds like insurance, but it won’t be, it’ll actually create a problem where none exists.

      Yes, you always want caulk or silicone in any change of plane. If you read around the comments a bit you’re sure to find one that asks why the grout is cracking in the corners and what to do about it – that’s why. The different planes expand and contract at different rates and in different directions. Silicone can compensate for that, grout can not.

  • Tyson

    Hi Roger,

    In your instructions for the shower pan you said the pre-slope needs to 3/4″ thick at the drain. I’m trying to reconcile that with the instructions from Sioux Chief that says to cut a 4 1/2″ inche hole in the subfloor and set the drain centered in that and resting on top of the subfloor. The drain has a 1/4″ lip. I understood the instructions from Sioux chief to mean that the pre-slop is 1/4″ inche thick at the drain. If it’s better to be 3/4″ do I just cut a 2 inch hole in the subfloor and raise the bottom of the drain to be 1/2″ above the subfloor to account for the 1/4″ lip allowing for a total of 3/4″ thick pre-slope at the drain? http://www.siouxchief.com/docs/default-source/technical-documents/installations/drainage/821-series—shower-pan-drain—installation-guide -thanks

    • Roger

      Hi Tyson,

      Yes, the two inch hole with the lower flange 1/2″ above the subfloor. Packing the deck mud under the drain around the pipe secures it.

      • Tim Moss

        Hi Roger
        I Love your site.
        I purchased 3 of your books.
        Please help, I’m planning to rip out the tub to make a 4′ X 8′ walk-in shower.
        Should I use the tub floor drain (almost centered) or the existing shower drain?
        I don’t like the idea of standing over the existing shower drain.
        ALSO – you advise to put an inward slope on a shower curb. How would that work with the installation of a glass wall (as pictured)?
        Thanks for listening.

        • Roger

          Hi Tim,

          You need to have a shower drain, a tub drain is 1 1/2″ and a shower drain is 2″.

          The slope goes to the inside of the shower from the outside, it should still be level from side to side. It doesn’t affect the glass at all.

          • T

            You are Awesome!
            Thanks for your advice.

    • John

      OK, let’s say some dummy cut the 4.5″ hole, glued the drain fitting, secured subfloor and caulked edges and installed 2 walls on sides before reading this. Is he screwed?

      • Roger

        Hi John,

        I’m assuming you mean you don’t have 3/4″ of mud at your drain? If that’s the case don’t worry about it. That is the spec in the book, but I have always gone to wherever the flange rests on the floor, normally 3/8″-1/2″. If that’s not the issue, let me know what the issue is.

        • Ryan

          Similar predicament. So the drain is installed, flush to the floor. Can you use the deck mud with some additive to have the 1/4 pre-slope go to nearly flush with the drain? Could you transition to thin-set closer to the drain? Is it worth cutting the drain out? And if so, could you build up a spacer to get the 1/2 space for mud against the drain for the pre-slope?

          Or, pull the board out and redo the drain?

          This site rocks, keep it up!

          • Roger

            Hi Ryan,

            Yes, you can. Although ideally you want to raise that drain 3/4″ so you have 3/4″ preslope at the drain. With the preslope it isn’t necessarily as imperative to have the thickness, provided you have a minimum 1″ at the drain on the top mud deck. The barrel (the part that screws in and out) can be unscrewed to accommodate that height. But you need that thickness there for the strength at the drain.

  • Valerie

    I have a cast iron pipe. I was thinking of chipping down the concrete enough to put a coupling on and install a PVC/ABS drain, in order to be able to do the waterproof liner properly.

    The other alternative is using the existing drain, and building the shower pan up to that height, then using a rubber membrane to seal everything.

  • Dave

    Hello Roger,

    I must say first off, that I have learned so much from your site and I can’t thank you and all of the other DIYers and pros for the great tips! My 36 year old house is one story on a concrete slab. I am redoing my shower and at the point where I am ready to put in my curb (Concrete of course) and my pre-slope. The bolts in the flange are rusted and the heads came off when I was trying to remove them. I have tried break free, cutting a slot in the bolt to see if I could use a screw driver, and tap-outs, all to no avail. My question is, can I drill 4 more holes in the flange at the same spacing as the current holes for new bolts (or something of the like) or do I need to break out the concrete and replace the entire flange? I have pictures but I am not sure how to upload them. Thank you.

    • Dave

      Ok….so I had a major senior moment there… Since the drain pipe is one piece all the way to the p-trap, what I am going to do is use and internal pipe cutter to cut of the old flange and put in a coupling and a new flange….. ahhhh, it sucks getting old.

    • Roger

      Hi Dave,

      You can drill new ones if you need to. It would be best to remove and replace it, but I know that isn’t always a viable option. Provided you only drill into the lower flange (that will be UNDER the waterproofing) then it’ll be fine.

  • Andrew

    Hi Roger,

    Speaking of drains, I’m trying to identify the types of drains, besides Kerdi, Laticrete Hydroban drain, or other bonding flange drains, that will work with a liquid topical membrane shower installation. In particular, will a clamp collar/ring drain (three piece) work for this method (ie. http://ebbe-america.com/product/e4024-pvc-clamp-collar-drain/)? If so, is there any special treatment needed on the clamp collar before tightening it down and installing the riser? Or, will the liquid topical membrane act as the “liner” in this scenario? I’ve contacted Ebbe and was told they just released a bond flange drain. However, it’s so new that no local supply stores have it and it’s not even up on their website.

    The reason I ask is because the Ebbe clamp collar style drain with grate is almost half the cost of a Kerdi drain. Looking to save where I can without sacrificing quality.

    Anyway, thanks for the advice!


    • Roger

      Hi Andrew,

      Yes, you can use that. Google ‘drain divot method’.

  • Marnie Rundiks

    Hi Roger, We are finishing a wet room. The cement shower pan (built by a contractor) is 6′ x 10′. We want to use 16″ X 16″ tile for the floor. Is that doable or would you suggest smaller tiles? Please advise! Thanks so much for all your great info – we have really enjoyed perusing your posts!

    • Roger

      Hi Marnie,

      You need to use a smaller tile which will conform to the slope of the floor. 3×3 is normally the biggest unless your floor is specifically fabricated for something larger.

  • Doran


    I bought and read your book Creating a traditionally waterproofed shower. Thanks! You recommended replacing the drain. Mine’s been in place for 50+ years and seems to want to stay there. how do I remove it without breaking anything? I have a picture I could send if that would help.


    • Roger

      Hi Doran,

      If it’s cast iron you need to get to the closest fitting beneath it and remove it. It can also be cut and a new fitting placed onto the pipe. Both are a pain in the ass. Cast iron sucks.

      • Doran

        You guessed it. Cast Iron in a concrete slab. Instead of bolts to tie the top half to the bottom, its one of those big hex numbers about 2 1/2″ across to put a pipe wrench on. My problem is I’m chicken. I tried to remove a cast iron cleanout on the exterior of the house with a pipewrench and I busted the pipe in two. Now what??

        • Doran

          I hit enter too quick – You said cut it…How? the cast iron drain is set into what appears to be a 5 or 6″ bell end which rises about 1/8″ above the slab. The bottom half of the drain (with the hex shaped top) appears to screw right down into that (The shredded remains of the original membrane are clamped down under it). There’s really nowhere to cut. The 2″ neck of the top half of the drain (with external threads rises out of the top of that.

          • Roger

            Plumbers have specialized tools to cut that stuff. If it’s not easily accessible that is your best bet.

        • Roger

          Call a plumber. :D Seriously. They have tools for stuff like that and it’ll take him less than an hour. Or you can dig out the pipe wrench and wd-40.

  • Seth

    The sink horizontal drain pipe between the sink and the down pipe in the wall has started to make a dripping sound when used in an upstairs bathroom. There is no evidence of the leak on the ceiling below.
    Is there any other way to repair the leak other than cutting into the ceiling below? Thanks.

    • Roger

      Hi Seth,

      I don’t think so – but I’m not a plumber, I’m a tile guy. :D

  • John

    I am about to install the mud bed over my concrete slab with box out access to the drain pipe and ran into a potential problem. My drain pipe is not exactly vertical. To be plumb it would need to be tilted over about 1/2 inch. If I install the Kerdi drain on the pipe as is it will not sit level. I am hesitant to force it with some sort of prop as I feel it may put too much force on the joints in the trap and eventually break. Is there a solution to this? Thanks.

    • Roger

      Hi John,

      You can either shim the drain pipe level or cut it down and attach a stub-up pipe with a fernco. The ferncos can be bent a little if you need to shim the pipe.

      • Paul

        Just had the same issue but wondered about putting a ferncos under the slab and out of sight. Your thoughts on this????
        I went with a few 22.5 degree joints and was able to obtain a level riser to drain.

        • Roger

          Hi Paul,

          If burying ferncos in concrete you need to use the shielded type.

  • John

    Hi Roger

    I bought your topical waterproofing a shower book some time ago.

    I am trying to figure out what kind of drain fitting I would use in the following scenario.
    Its new construction with 1″ plywood (on 12″ joist centers) pre-slope (don’t ask, I like working with wood). I will thinset 1/4″ CBU and apply 2-3 coats of RedGard with recommended joint/corner reinforcement. I want to use a 4″ square drain connected to 2″ ABS below. My concern is the type of drain fitting to use so that I can RedGard-it and have a good waterproof system (without mortar bed etc).

    Can you recommend the generic type of drain fitting (so I know what I am asking for), and some brand/part names?



    • Roger

      Hi John,

      If you are using redgard without a mud deck (??? – not a good idea) then you need a topical drain. There is no way to tie in the weep holes in any regular three-piece drain. Schluter kerdi-drain or Laticrete’s hydroban drain are the two most readily available.

  • Bernie

    The shower in our brand new house master bath had been leaking and we didn’t realize it until we saw the water line on the ceiling of the floor below. The water was coming from under the two by four on the flat that is the base for the wall that divides the back of the tub and the shower wall. We are able to see this from the access panel in the side of the tub. To me that would indicate the water is between the membrane and the sub floor. If you run your hand along membrane to the corner its dry. The flooring in the bath are those heavy vinyl tiles with some sort of synthetic grout between them. We noticed that in an area adjacent to the shower the grout lines were bubbling some brown material and when we cleaned them off the grout line eroded compared to the lines farther away. The lines nearest the shower are leaving dark lines on the bottom of the bath mat closest to the shower. I suspect a penetration in the corner where the curb meets the wall and perhaps the water ran under the floor tiles and was coming up in the grout lines of the floor. The membrane is only up the wall about 5-6 inches. This is under warranty so the builder had the plumber come out first to confirm that no plumbing was leaking. Then the original tile sub contractor came out (we weren’t thrilled with his work even before this) and chipped out some grout that had cracked on the opposite corner and then used matching color caulk and went around the perimeter where the floor meets the wall and up the walls in the corners with the caulk. We let it dry for 24 hours and now the area is staying dry. So in your opinion is the problem solved for good or is the caulk a band aid for a bigger issue that will come back to haunt us after the warranty period is over and the caulk has time wear out? I have pictures but can’t figure out how to place them in this message.

    • Roger

      Hi Bernie,

      It is simply a band-aid. The problem is still there. All the caulk did was slow the water which was getting to the area of the shower floor which is leaking. It is not permanent – at all. The problem is that your waterproofing membrane is compromised somewhere, caulking the tile only slowed the leak so it can do more damage before you notice it again. And you will notice it again, it’s only a matter of time.

      • Bernie

        Thanks for the reply Roger! I thought that was going to be the answer.
        The big question now is what needs to happen to properly repair it and will the builder be willing to fix it the right way? I would assume it involves tearing the shower floor out and taking the tile off part way up the walls as well. Also do you think the water could be wicking under the vinyl floor tiles and disturbing the grout as I described?

        • Roger

          Yes, removing and replacing the shower floor with a properly built deck, and that will require removing a couple feet up the wall. And wicking is exactly what’s happening with your vinyl and grout.

  • Steve

    Hello Roger,
    Does Schulter make a smaller diameter mixing valve seal? The one that comes with the Shower kit is a 4.5″ diameter seal which is over-sized for the square (3.5″) plaster guard on the delta mixing valve that I’m installing.
    Also, do they make a smaller seal for a diverter valve w/no plaster guard.

    If no to both, do you have an alternative method for sealing around diverters and mixers when the seals are over-sized or not available?

    Thank you for your reply.


    • Roger

      Hi Steve,

      No, they don’t make smaller ones, but a larger one will work fine. Alternatively you can do this: Sealing tile penetrations

      • Roger

        Hey Steve,

        Sorry, I just realized I gave you the wrong link yesterday – this is the one you need: Tile penetrations

  • Amber

    We have had to re-do our shower due to the un-intelligent people that had originally put it in before we bought our house and need some assistance from the elf! We have ripped all of the old tiles out and replaced the cement board. We are using the Red gard sealer but came to a problem with the drain. The floor of the shower is a concrete slab which they put a regular shower drain in and we need to know if we need to dig out the concrete to re-do the whole drain or if there is a way to use what is there to make a good drain. From things we have read on the internet, it looks as though the drain has to be entirely replaced and we’d have to break out the concrete to get to the floor drain in order for it to sit correctly on the tiles (if and when we get to that point). If this makes sense. We have been procrastinating this project for over a year and are in need of help! Thank you! :bonk:

    • Roger

      Hi Amber,

      You need to replace the drain with a topical drain. Schluter (kerdi drain) and laticrete (Hydroban drain) both make one. You can utilize a regular three piece drain with the divot method (google it) if you want to, but it may not be possible with your drain. It just depends on what you have.