How to find existing radiant heat tubing in cement slab

[mjeselskis]

Our house is built on a 6" slab with rebar and radiant tubing. I didnt build the house so I'm not sure how deep the tubing is set in the slab. Now I'm looking at remodeling and need to cut a few holes in the slab for plumbing, which leads to my dilemma... I need a reliable, and cost effective, way to locate the radiant tubing before I fire up the pavement saw. Anyone have any good methods for locating the tubing?

So far I've heard a few suggestions such as using a IR thermometer when I first fire up the boiler with a cold slab to look for temperature differences, and/or using a thermal imaging camera to try to see the heat delta as it warms up. Just not sure if either of these will work, plus I currently dont have any of these tools to do it.

[Holmes]

If you can turn up the water temp in the radiant system some and turn the system on, pour some water on the bare concrete and see where it dries up first . That will be where the tubing is. If your system is on now give it a try.  The tubing usually is at the bottom of the cement tied to the rebar. It would usually be spaced 12" on center.  If you do cut the tubing  you can put mechanical couplings on the pipe for repairs. It will be best to use the same name parts as the tubing.

[submarinesailor]

The best way is to get a Certified Infrared Thermographer to scan the floor with the system up and running.  The greater the delta T you can get, the better.

While I was working as thermographer, I was able to locate wall studs and ceiling joints using a GOOD IR camera........NOT A SCANNER.  Under the right conditions, I could locate rebar in a slab...again using a good IR camera.

Bruce

[mjeselskis]

Thanks for the suggestions. I'll try the water trick first as that sounds pretty simple, although it may be time consuming waiting for it to dry...

Bruce,
I have seen/used a color thermal imaging camera that gets used to look for hot spots in electrical panels. Is that the type of device you would recommend? How much would it cost to hire a pro to do this type of job? Its just one room, about 8x8 that needs to be marked up.

[beenthere]

A little "time consuming" is a lot cheaper than hiring out the job with expensive equipment. Seems to me... ;)

[mjeselskis]

A little "time consuming" is a lot cheaper than hiring out the job with expensive equipment. Seems to me... ;)

Yup, I agree

[Don_Papenburg]

mark out your proposed cut, sawcut the  area only an inch deep .  Use a mason chisel and mall  to bust out the concrete in layers of 1 to 2 inches .  the pex tube is very forgiving of a bump or two with a mason chisel as long as it is not real sharp . Blunt the cutting edge a little before starting . When you find the tubes work parralel to them.

[florida]

This is very easy to do. Simply use a hammer  drill and 1/8" bit to drill a 3" deep hole. You are 100% guaranteed to hit the tubing!

[mjeselskis]

This is very easy to do. Simply use a hammer  drill and 1/8" bit to drill a 3" deep hole. You are 100% guaranteed to hit the tubing!

Trust me, that thought has crossed my mind several times.

Along with the methods mentioned, I've also wondered about a metal detector if I knew that the tubing was tied to the rebar.

[Holmes]

Usually the tubing is tied to wire mesh that has 6" squares. I have not seen many rebar installations in houses. A metal detector will not tell you which wire the pipes are tied to

[sprucebunny]

I got a good IR thermometer for Christmas last year. I'm pretty confident that I could cut a 6" square hole in my radiant slab and miss the tubing. ( It's on 12" centers). There is only about a degree difference between where the tubing is (or seems to be) and the space in between. Once you locate one run, the others should be mostly parallel. When I put the pex down, the first row around the perimeter is 6" spacing... and there maybe places in yours where the pattern is a little different, too.
I would want to start with a cool slab and hot water more than once and pencil my findings.

Another thermometer that might work is one of those flat ones that you stick to the side of a propane tank... it seems to me there was one like that for people's foreheads, too.

[jdtuttle]

If there was a building permit issued the file may have a layout drawing or pictures of the installation. When I installed it in my house I took pictures and copies are at the building codes office.
jm

[wheelinguy]

I second Don's idea, inexpensive and the pex can take some pretty good abuse.

[mjeselskis]

Usually the tubing is tied to wire mesh that has 6" squares. I have not seen many rebar installations in houses. A metal detector will not tell you which wire the pipes are tied to

The guy that we bought the house from liked to have things built extra strong, thus the rebar and 6" slab. It sounds like my options are the water trick, thermometer, thermal camera, or cut and chisel.

I can check with the builder and/or town office but it's a small town that shares a building inspector with other towns so there's not much paperwork involved normally....

[NWP]

I am in the same situation.  I zip tied my tubing to the rebar when I installed it.  It's about on 12" centers.  When I finish my basement, I'm afraid I'll shoot a nail or screw through the bottom plate of my walls and hit the tubing.  I think I'm going to try a thermal camera and use a marker to mark the tubes in the floor around where my walls will go.  Keep us updated and let us know how things work out.

[WmFritz]

When I finish my basement, I'm afraid I'll shoot a nail or screw through the bottom plate of my walls and hit the tubing.  I think I'm going to try a thermal camera and use a marker to mark the tubes in the floor around where my walls will go.

When I built my interior walls on my radiant slab, I cut my studs nice and snug. Then I used Liquid Nail on the bottom plates with no fasteners. My only concern was how well the adhesive would stick to the pressure treated plates but, they are plenty solid.

[jueston]

When I finish my basement, I'm afraid I'll shoot a nail or screw through the bottom plate of my walls and hit the tubing.  I think I'm going to try a thermal camera and use a marker to mark the tubes in the floor around where my walls will go.

When I built my interior walls on my radiant slab, I cut my studs nice and snug. Then I used Liquid Nail on the bottom plates with no fasteners. My only concern was how well the adhesive would stick to the pressure treated plates but, they are plenty solid.

that is how i would do it if the nails are a big concern, liquid nails and the like are all polyurithane adhesives and will stick to wet treated wood real well. but you could also go with nails that are only 2.5 inches long which would only penitrate 1 inch and be safe...

[gunman63]

Are u sure its even in the concrete,  the best way is foam insulation, pex attached to that, then sand,  then concrete. all depends on how they  did it

[mjeselskis]

Are u sure its even in the concrete,  the best way is foam insulation, pex attached to that, then sand,  then concrete. all depends on how they  did it

I've confirmed with the prior owner that it is in the concrete, but that's about as far as I've got. Hopefully I'll get a chance to find it in the next few months.

[sbishop]

Quote from: WmFritz on January 03, 2013, 06:44:47 pm



Quote from: NWP on January 02, 2013, 11:08:27 pm

When I finish my basement, I'm afraid I'll shoot a nail or screw through the bottom plate of my walls and hit the tubing.  I think I'm going to try a thermal camera and use a marker to mark the tubes in the floor around where my walls will go.






When I built my interior walls on my radiant slab, I cut my studs nice and snug. Then I used Liquid Nail on the bottom plates with no fasteners. My only concern was how well the adhesive would stick to the pressure treated plates but, they are plenty solid.



that is how i would do it if the nails are a big concern, liquid nails and the like are all polyurithane adhesives and will stick to wet treated wood real well. but you could also go with nails that are only 2.5 inches long which would only penitrate 1 inch and be safe...

This is exactly how i did the whole house as i'm on a slab....I took out my son's metal detector that he got for Christmas and it is picking up the wire mesh...i get a beep every 6" going across the floor....my pex was 6" on the outside for 2 rows...then 12" rows....

Good luck, like others have said...pex is strong!

Sbishop

[Randy88]

I'd need some more information as to exactly what your trying to do in the concrete in the first place, put holes in it for what exactly? to go where exactly? and how big of holes exactly?   

But I"m guessing here on all of the above and assuming you want to do plumbing of some sort with water, you'd then have to go outside and undermine the the house to hook it up, or if your putting the lines inside from inside somewhere, I'd opt for plan b completely on both issues, if your working inside a room for example and want to hook up a toilet or something or a waterline and drains for a sink that will end up in the middle of a room after the remodel, again I'm only guessing.   I'd try a different approach, I'd overlay the current concrete with another layer with my plumbing in that if I absolutely had to, for a toilet or something, I'd do a false floor out of wood for the toilet to sit on and not mess with the infloor heat at all on any occasion for any reason.   Remember anything you cement in the floor, will eventually need repair due to wear out, rust out, leaks or someone else's design change of the house remodel and need to be moved again.   Your not just going to do this once, but every time you need to fix or change it or repair it.

If your remodeling the house inside for something that needs plumbing, redesign it so that the plumbing is on or along a wall somewhere, and make that work to your favor, again only guessing as to what your doing, but build a false wall inside an wall to enclose the plumbing into that to hide it.   

Remember everyone's sure fire solution to the problem so far, involves an educated, higher tech, guess and that's about what it is, if anyone's wrong, you get to redo the entire floor anyhow of the whole house or opt for a different heating option for the house, I'd opt right away with a sure fire solution of a plan b altogether, not mess or worry about the heat tubes by not messing with the existing floor, that way, you can't hit the tubes with anything, but without more information as to what, why and how you need to be into the cement floor exactly I can't help much with a plan b.    Just an observation and idea to ponder.   

[Randy88]

Oh I forgot to mention, but if your doing a false wall inside the house, like some mentioned with liquid nails, I'd instead, form up for a concrete wall, scuff up the floor where its to sit, and pour a concrete false wall on top of the concrete floor and put my bolts in that to hold the 2x's to so I could build off of that, again its just an idea of how I've done things in the past, I'd never drill into the floor with nothing more than an educated guess, unless someone who installed it, did good  job of mapping it, as for being exactly on the mess or rebar lines for the water lines, that's a very nice idea indeed, but I've installed and watched enough others install the pex, and I can testify that's not entirely how its actually done 100 percent of the time, good theory, but theory doesn't necessarily correlate into reality all the time, most of it or even some of the time, its "kinda" however it works out is actually how its done by most, remember, they're trying to keep the lines equal length, not necessarily equal spacing on the wire mess, total footage of piping being the same, not equal spacing of the lines, 330 feet is the magic number to hit with each line, why, because pex comes in usually 1000 foot rolls, divided by three, no waste at the end of the job is the idea and its cemented in, thus nobody sees exactly how its done to achieve that number or goal.   With all lines being the same length, the heat is distributed equally through the slab, if some lines were shorter, they'd pump the water through those easier, causing them to be warmer than the others, that the homeowner would notice over time, not the spacing or how the lines were placed in the floor that they can't see anyhow.   Just some information to think about and cause discussion about, as for using a metal detector and 'guessing' all lines were hooked to the mess at those locations equally spaced, good luck and don't worry, you'll know when you hit one and it won't take long to find out either. 

[mjeselskis]

Oh I forgot to mention, but if your doing a false wall inside the house, like some mentioned with liquid nails, I'd instead, form up for a concrete wall, scuff up the floor where its to sit, and pour a concrete false wall on top of the concrete floor and put my bolts in that to hold the 2x's to so I could build off of that, again its just an idea of how I've done things in the past, I'd never drill into the floor with nothing more than an educated guess, unless someone who installed it, did good  job of mapping it, as for being exactly on the mess or rebar lines for the water lines, that's a very nice idea indeed, but I've installed and watched enough others install the pex, and I can testify that's not entirely how its actually done 100 percent of the time, good theory, but theory doesn't necessarily correlate into reality all the time, most of it or even some of the time, its "kinda" however it works out is actually how its done by most, remember, they're trying to keep the lines equal length, not necessarily equal spacing on the wire mess, total footage of piping being the same, not equal spacing of the lines, 330 feet is the magic number to hit with each line, why, because pex comes in usually 1000 foot rolls, divided by three, no waste at the end of the job is the idea and its cemented in, thus nobody sees exactly how its done to achieve that number or goal.   With all lines being the same length, the heat is distributed equally through the slab, if some lines were shorter, they'd pump the water through those easier, causing them to be warmer than the others, that the homeowner would notice over time, not the spacing or how the lines were placed in the floor that they can't see anyhow.   Just some information to think about and cause discussion about, as for using a metal detector and 'guessing' all lines were hooked to the mess at those locations equally spaced, good luck and don't worry, you'll know when you hit one and it won't take long to find out either.

Appreciate the good info. I am remodeling as you guessed. I have an area that used to be garage and I'm putting in a bathroom. Sink is easy, piping goes into the wall and into existing piping. Shower and toilet are a whole different story. Now I know I can do a false floor or pump-up toilet, but i really want to avoid that. Don't want to step up from the rest of the house into the bathroom, and dont want to deal with the expense and maintenance of the pump up toilet.

So... the bathroom is approx 4 ft in from the edge of the house. My plan is to cut a hole in the floor, approx 1'x1' where the toilet will sit, then cut a hole for a 6" steel pipe in the frost wall. I want to sleeve that pipe in under the slab to where the 1x1 hole is in the slab. I will then run my 4" pvc pipe through that and make my connections below the slab and setup the flange for the toilet. The shower can be a little elevated and I'll find a way to make the connection into the same 4" pipe under the toilet. Just need to plan for traps and access to a cleanout if necessary. I'll have foam insulation board over the pipe where it exits the house underground to deal with possible frost concerns.

As far as maintenance, I don't see it being that much different than any house that is built on a slab. Once the piping is in place and the slab is poured, you are stuck.

Look forward to any other inputs, I appreciate the other points of view.

[Randy88]

Not physically seeing what your doing in person, is there any way you could put the toilet on an outside wall and just get a shorter toilet and have that mounted on a false wooded floor pedistal somehow and once outside, you could insulate the lines and put that in any kind of box you want to prevent freezing.   How far away from the existing sewer lines are you going to be, do you have enough fall to make this work for the line drainage?    I'd never used a steel line for anything under a cement slab or in it either or associated with a sewer system period, not to sleeve with or use as a sewer line, only pvc.     

In order to cut a foot square hole in the floor and as long as you need to, to get it outside the house and as deep as you need to go, I'm not seeing how your not going to hit a line somewhere, either where it makes the bend at the walls to continue the loop back to the floor or in your foot wide trench somewhere, most lines are on foot centers at most, most are less than that in all reality, depending on the cement and plumbing crews that did the lines.   

If your heart is set on doing it in the cement, do some homework to figure out who put the stuff in and find out how they did things at the time this was done, over the years, as the infloor heat progressed in popularity, so did the recommendations on installing it, also came into play, the experience of the crew, knowledge of the concrete people doing the pouring, and everything in between, no two crews on anything do anything alike.  Not even today, most around here put lines in less than one foot on centers, and have lines closer to the walls, also something to ponder is how many lines run lateral along the walls, depending on how many feed lines go the manifolds, you could have up to or more than a dozen lines inches apart along the walls depending on where in the house this is located, not sure how well the heat signature idea will work in those locations.    Some back when in time ran the return heat lines for multiple lines back along the walls and intertwined them in sequence as they went laying them out before cementing.  Like I said I've seen it all done over time, depending on who and when it was done and how good of a job they did, I've even seen the lines bubble up as it was poured and the cement crews just pushed it under the top of the concrete, being only an inch or two deep in places.   Also a lot of crews didn't tie them to the lengthwise portion of the mesh, if they needed it closer for spacing to come out, they'd tie them to whatever spacing they needed, some even stapled them to the insulation board and then just laid the mesh over the top to hold it all down, in no random order at all in relationship the the mesh, some ran more than one mesh layer depending on how thick the concrete was, or how fussy the cement crew was about strength and quality of their work.   If your going on a treasure hunt so to speak looking for lines, I wish you the best of luck, I'd never do it because I'm not lucky on anything, no matter how positive I was about the lines locations, even with maps and pictures.   Just my two cents worth.   

[mjeselskis]

Maybe someone already suggested it, but I just searched for "rear exit toilets" on google and came up with all kinds of options. I thinK I may have just solved the problem. These toilets have the piping coming out the back at approx 7" off the floor. The toilet will be against a wall that is dead space below the stairs so I can run the piping through the wall into that dead space and then go through the frost wall and underground. I will build the shower with a false floor to run the lines through that same dead space on top of the cement and tie into the toilet line that goes out through the frost wall.

I'm sure I'll run into obstacles, but i may not have to cut the floor after all... which would simplify the whole project

Just one examplehttp://www.signaturehardware.com/product20261?utm_medium=shoppingengine&utm_source=google&utm_content=Bathroom-Toilets&adtype=pla&gclid=CMfmyb6q6bQCFYl7QgodTF8ASg