Replumbing a home - PEX in furnace duct

Real Estate Investing Mobile Homes & Mobile Home Parks
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I’ve previously read here about running the PEX pipe inside the furnace duct when re-plumbing a home - both as a way to keep the pipes from freezing in the winter if the belly is all torn up, and as an easier way to get the piping from one end of the home to the other. I haven’t tried it yet but am thinking about it. I have a question or two, though, and couldn’t find any info in the archives.

So, what’s the trick for getting the tubing to run through the furnace vent without trying to curl back up on you? My idea would be to use an electrician’s “fish tape” and pull it from one end of the other.

What about"T’ing" off the mainline? Do you have to cute a big hole in the duct work and then tape/patch it back up? That’s the part of the plan I’m not excited about. Not just because it doesn’t sound fun, but because I would rather not be tearing up the duct work.

I’ve used PEX to re-plumb several homes (in the belly when it’s intact, or inside the home itself when possible) so I generally know what I’m doing. I just haven’t tried it IN the duct work . . . but I like the idea.

Thanks,
Michael(KCMO)

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Michael, I would not leave a belly “all torn up” it is a huge heat loss. Not to mention a rodent attractor and against code. Kill 2 birds, while you are under there fixing the belly, re-plumb.

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[QUOTE=Michael(KCMO);883015]I’ve previously read here about running the PEX pipe inside the furnace duct when re-plumbing a home - both as a way to keep the pipes from freezing in the winter if the belly is all torn up, and as an easier way to get the piping from one end of the home to the other. I haven’t tried it yet but am thinking about it. I have a question or two, though, and couldn’t find any info in the archives.

So, what’s the trick for getting the tubing to run through the furnace vent without trying to curl back up on you? My idea would be to use an electrician’s “fish tape” and pull it from one end of the other.

What about"T’ing" off the mainline? Do you have to cute a big hole in the duct work and then tape/patch it back up? That’s the part of the plan I’m not excited about. Not just because it doesn’t sound fun, but because I would rather not be tearing up the duct work.

I’ve used PEX to re-plumb several homes (in the belly when it’s intact, or inside the home itself when possible) so I generally know what I’m doing. I just haven’t tried it IN the duct work . . . but I like the idea.

Thanks,
Michael(KCMO)[/QUOTE]

Michael,

While keeping the water lines warm is important I don’t see the advantage of fishing them through the duct work. It seems to me that any future repair would be very hard to troubleshoot if you have T’s and turns throught the duct work. I understand that one might argue you just cut each end and pull the whole length out but I’m not so sure.

I also wonder about what future water damage might do the the ducts themselves since a small pinhole type leak might go undetected for some time.

I could understand if you wanted to run your lines run along the ducts but not inside them. This is how many homes are manufactured. This keeps the lines warm and gives you access to them in the event a repair is needed.

Repairing the underbelly and installing insulation and heat tape may be your best option.

I have run water lines inside homes and although it is not necessarily pretty even when we work hard to hide the lines, I know I will be glad if I ever have to fix them and all I have to do is work inside the home. Being that they are inside they should remain warm and any leaks should be quickly detected by the tenant.

In most cases I find it easier and faster just to run to main 3/4" lines (one hot and one cold) side by side down the length of the home along the heating duct if possible, insulate the lines with the sleeves, add heat tape and use 1/2" T’s to run the lines up through the floor to the faucets etc.

Honestly with pex this approach takes very little time at all. I do like the 3/4" T’s that are 3/4, 3/4 to 1/2" as they make for fewers transitions (less weak links) and faster installation.

Tony

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Tony,

I’m surprised . . . I thought it was you that had originally mentioned the idea of running them inside the duct work. My memory isn’t what it used to be, apparently.

Well, the job is 3/4 done now (planning to finish up this morning) and I’m actually quite pleased with the result.

I don’t disagree with any of the advice/insight you offered but in this case it wasn’t quite as practical. Don’t worry. I have 4 more complete re-plumbs to work on - hopefully before the winter turns bitter - so your advice will be put to good use, I’m sure.

Michael(KCMO)

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So Michael, did you actually run them THROUGH the ductwork? If so how did you make tees inside it?

Steve

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[QUOTE=Michael(KCMO);883033]Tony,

I’m surprised . . . I thought it was you that had originally mentioned the idea of running them inside the duct work. My memory isn’t what it used to be, apparently.

Well, the job is 3/4 done now (planning to finish up this morning) and I’m actually quite pleased with the result.

I don’t disagree with any of the advice/insight you offered but in this case it wasn’t quite as practical. Don’t worry. I have 4 more complete re-plumbs to work on - hopefully before the winter turns bitter - so your advice will be put to good use, I’m sure.

Michael(KCMO)[/QUOTE]

I may have chatted up such an idea, I do that kind of thing a lot but I have not tried to install plumbing in the ducts themselves. I don’t like working with ducts anymore than I have to as they seem to leak more than not once messed with.

I have replumbed a doublewide and a singlewide by running all the lines in the corner where the ceiling meets the walls of the home and boxed them in. In the doublewide I ran the through all kinds of hidden spots but It was more work than was probably necessary.

I think I had been through a couple of very cold, very wet water breaks that left me freezing and laying in puddles of cold water repairing broken water lines and finally had enough so I did the next 2 inside the home. That was several years ago and I have not this since.

I like pushing the envelope of ideas and glad you are giving something new a try. We can all theorize the pros and cons but until someone actually does it, none of us will ever know for sure.

Please let us know how it all turns out.

Tony

Ps. One motto I have come to live by is “hey, let’s try it out on a singlewide!” I figure you can’t go too wrong on one and you might just find a whole new plan.

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PEX in the Duct - The Result

Yes, Dr B, I ran the main, 3/4" line through the main trunk duct work.

First, I poked a small hole in each end of the duct and ran an electrician’s “fish tape” all the way through. Having left the red/blue PEX stretched out in the home overnight, most of the worst curly-q’s were straightened out of it. Using one of those chinese handcuff looking thingies and some electrician’s tape, I attached the fish tape to the two PEX lines and pulled all the way through the home in a matter of minutes!

There was only one connection in the middle of the home . . the one for the kitchen sink. I cut an “X” in the bottom of the duct and a small, small hole in the side to push through a 1/2" PEX. After cutting in and crimping the “T” I closed up the “X” cut and taped it solid with duct tape (NOT “duck” tape. I used the special tape for duct work).

On either end of my main run were two baths, laundry room & water heater. I left the 3/4" PEX sticking out the ends of the duct work and taped up around it. I used the 3/4-1/2-3/4 “T"s that Tony described and essentially built a manifold to run a 1/2 line to each fixture. Doing this, I was able to keep most of the 1/2” runs from the manifold between one or two pairs of floor joists - easy to insulate, and all my fittings are together - making any future repairs (unlikely) that much easier.

So, there you go. The whole rough-in, hook to meter line & plumb the w/h took about 5 hours with no help. All that’s left is to hook up to each fixture.

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Tony,

Thanks for the info. I’ve plumbed several homes by running the PEX inside the home. That’s definitely the preferred way to go! It’s quick and easy to do; I don’t have to crawl around in mud, 'possum poop, cold & cobwebs; I don’t end up with knots on my head and you get work inside, up where it’s warm!

After having experimented with this method now, I think I like it as a second choice. I described it in further detail on up the thread in response to Dr B’s question. And, yes, this was a singlewide. :slight_smile:

Michael(KCMO)

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Thanks Michael,
It sounds like an ideal situation where most of the plumbing is at the ends of the home (frequently found). I too have plumbed at the corner of ceiling and wall on the inside. I found it a PIA to make bulkhead cover boxes. I will consider TTD (through the duct) plumbing as an option from now on.

BTW was there no W/D hookup?

Steve

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[QUOTE=Dr B(OH);883053]Thanks Michael,
It sounds like an ideal situation where most of the plumbing is at the ends of the home (frequently found). I too have plumbed at the corner of ceiling and wall on the inside. I found it a PIA to make bulkhead cover boxes. I will consider TTD (through the duct) plumbing as an option from now on.

BTW was there no W/D hookup?

Steve[/QUOTE]

I agree that boxing in the plumbing to hide it was a bit of a pain. For the most part I was able to hide it but some boxing was required. I actually had an old handyman take care of that part (this was years ago).

Lately if I have to replumb I do as I think I wrote about above and run 2 main 3/4" lines with 1/2" connections through the floor and to the faucets etc.

Insulate(wrap if below the underbelly) and heat tape. If the skirting is in good shape this seems to do the trick but keep in mind that I live in North Carolina so our winter weather is much more mild than many who post here.

Tony

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I’ve always wondered if you can get a thermostat control for heat tape. How do you guys control when it is on or off?

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the heat tape has a sensor on it that turns the heat tape on when the pipe falls below a certain temp.

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As I dry off and reflect on the water breaks I have had recently, and in the past, I am reminded of the true common theme.

My water lines, now mostly pex always freeze and break in the same place, at the spot where the main comes out of the ground and before it transitions into the home. In most cases this pipe is 3/4" PVC that comes out of the ground but I have run into other materials from time to time.

Bear in mind that I live in a very mild climate here in North Carolina but we do get winter cold snaps.

For the most part, my active homes (rented) I do not have pipes sitting with water and cracking when power goes off or out. Even homes that have sat for periods of time in cold weather without power have been undamaged because they had pex.

Where the damage occurs is that 18" or so from ground to Pex conversion that freezes and breaks. Most of these are in parks which means that the cutoff is the weaklink in this set up. The only cutoff to the unit is that 3/4" PVC ball valve that is installed about 12 inches above ground. For some reason in my one park the lines are burried almost 4 feet down which is way overkill here but makes it difficult to install other cutoffs that can be readily reached.

When heat tape fails or insulation is damaged around this vulnerable 12" to 18" inches of PVC pipe, trouble occurs.

If I am converting to pex, I am discovering there is no real worry about that rest of the pipe under the home so long as I focus my attention on keeping the 18 inches of main PVC protected. If I have that part protected the homes seem to be safe from freezing damage. I still insulate the pex lines, usually by either placing them in the underbelly near the duct work or by extending the heat tape some on the cold water line and covering the rest in the tubular insulation.

That magic 18" or so is the area that needs my utmost attention and when I fail it I know it and am always reminded at the worst possible time (frigid night) and worst possible way (laying in a puddle of cold water on a frigid morning making the repair).

The rest now appears to me to be overkill. I believe it would be wise for me to create a better model for insulating and protecting the first 18 inches of water line that exits the ground.

I have seen one example where corrigated piping was split down the middle and used to enclose the insulated this 18" of pipe. This rigid exterior should protect the pipe well from animals and drafts while the intact insulation or heat tape can keep the pipe from freezing.

Tony

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Tony,

where do you place your heat tape? Is there a way to shorten the tape or modify its placement so that it can be used in the critical area? The shortest tape i see in Lowes is in 12 foot lengths.

I experienced a break where the pipe first exits the ground, during our first freeze, in this case it was the metal pressure reducing valve that froze and split. I replaced the valve and added missing insulation, but this area froze again. No heat tape.

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Plumbing supply houses have heat tape in rolls that you cut to length and install the ends.
As far as the shutoff valve and PVC pipe, I would lower it to just below the ground inside a 6"-8" pvc pipe “crock” that goes about a foot or so below ground level around the supply line. That way you can just cover it with a piece of insulation and it will never freeze.

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[QUOTE=Don-NY;883845]Plumbing supply houses have heat tape in rolls that you cut to length and install the ends.
As far as the shutoff valve and PVC pipe, I would lower it to just below the ground inside a 6"-8" pvc pipe “crock” that goes about a foot or so below ground level around the supply line. That way you can just cover it with a piece of insulation and it will never freeze.[/QUOTE]

I agree that this should be the best way to be assured that the pipe does not freeze at the conversion from ground (typically PVC in my properties) to above ground PEX.

I have run into a spot where this type of “crock” was used and unfortunately this “crock” was made of metal and about 8 inches in diameter. It was too narrow to make the repair I need so I had to dig around this “crock” and cut it vertically with a sawzall (all while crouched under the home). Not to mention that this is the low spot of the land now and repeatedly filling with water as fast as we can pump it out with a wet vac.

Challening? Yes.

Fun? Na

Right way to do it? Almost.

Your way is best.

Tony

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Tony, I’ve Been there. Maybe a 5 gallon bucket would be better, more room. I had a broken pipe (Copper) in an 8" crock I bought a cheapo pipe cutter, cut the t handle off and used pliers to tighten it. It was a PITA but it cut the pipe and then I used a “shark bite” fitting for the repair. Probably took the same amount of time but riding around in the truck fetching the cutter and fitting is more fun than crawling around in the mud and gave the water time to drain out of the crock.

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[QUOTE=Tarheel T;883841]Tony,

where do you place your heat tape? Is there a way to shorten the tape or modify its placement so that it can be used in the critical area? The shortest tape i see in Lowes is in 12 foot lengths.

I experienced a break where the pipe first exits the ground, during our first freeze, in this case it was the metal pressure reducing valve that froze and split. I replaced the valve and added missing insulation, but this area froze again. No heat tape.[/QUOTE]

Lowe’s does carry a 6 foot heat tape for something like $22 or you can buy the 12’ and 18’ for a few dollars more. I usually buy the 12’ if there is any water line below the underbelly and then run the heat tape in a straight line along the pipe until I run out of heat tape. I then cover any remaining pipe in the black, tube like insulation and tape it closed around the pipe.

One common mistake (done this myself) is to overlap the heat tape on itself. Don’t do this. It will melt itself (guess how I know) and short out the heat tape, allowing the pipes to freeze.

Live, learn and freeze while fixing the mistakes is my motto.

Tony

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A few years ago, I owned an old farm house with a jetpump in small shed near the well. I got concerned about the black plastic pipe freezing so I ran a heat tape along its length with electrical tape every 12" or so. I then covered it all loosely in polyethelene. Coldest night of the year…got a call, no water. When I went to check I found the black plastic had melted and collapsed. I suppose it was because I left the termostat exposed. Keep that in mind.

JDPugh

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These are exactly the reasons I do not heat tape any of my POH’s I use insulated flexible duct instead and run pipe straight up into the heated floor space.
Here are the reasons I only use the professional heat tape from the supply house on other homes.
I always have exactly the right length on the truck
It does not melt pipes
You can overlap it several times and it will not melt itself
You can use the split foam insulation which goes on a lot faster than wrapping. (with most tapes you have to use the fiberglass wrap with saran wrap over that or the tape will melt! What a PITA)
The cord is about 4 feet long so easier to reach the outlet
It looks different than home depot tapes, more like professional materials justifying the price of the job.
And again. If it happens to fail on a cold Sunday evening I am sure to have the right length on the truck.
Invest in some!