Replumbing double wide with (mostly) intact underbelly

[dieselfuelonly]

Hey all, I'm located in NC and have a 1989 1000sq ft double wide manufactured home that I intend on replacing the polybutylene pipe with PEX. With the exception of underneath the laundry room on one end of the home, the underbelly is mostly intact and I'd love to keep it that way.

Just looking for advice on the best way to go about replumbing this house. I have a 1000sq ft garage that butts up against one side of the house that I currently have a 500 gallon storage tank for a low-yield well in, and I'd like to move the water heater there as well during this process and possibly add a recirculation line.

All the plumbing is on one half of the house.

So far I've seen 4 main options:

1. Cut holes in the underbelly to fish the PEX through above the underbelly/insulation, cutting large enough holes to make all the crimps teeing off the main 3/4" lines. Then repair the underbelly the best I can.

2. Remove the whole underbelly and make a new one that hangs underneath. Much easier said than done, although it would make the plumbing itself MUCH easier.

3. Cut strategic holes in the floor and fish the PEX through from above. All of the flooring I would be cutting is is linoleum, so a new piece would have to be put down in the rooms. Some rooms just have the little stick-on tiles which would make this somewhat easier to repair, others not. This would require at least 4-5 holes in the floors and I guess just hoping I cut in the right spot (appears the existing plumbing is run along side the heating duct on one side).

4. Run the PEX below the underbelly and do all the teeing off underneath, then stab directly up through the underbelly to where the connections need to be made. Easier to plumb and less damage to the underbelly, but would require all the PEX to be insulated plus heat tape maybe as the winters here can get down in the teens.

Honestly, since I'm on well water the polyb pipe has held up fine. But the flow to many of the fixtures sucks as it's only 3/8" pipe. I figure I'll have to replace it all at some point anyway, so might as well have a plan before something major finally goes.

Thanks for any advice.

 

[Tuttles Revenge]

What material is the underbelly? Aluminum or steel? How is it secured? screwed to the bottom or laying on top of something?

If that were me doing the work, and I'm imagining that the underbelly is an aluminum skin, I think I would cut strategic holes in the underbelly and patch accordingly.

 

[Sponsor]

 

[dieselfuelonly]

What material is the underbelly? Aluminum or steel? How is it secured? screwed to the bottom or laying on top of something?

If that were me doing the work, and I'm imagining that the underbelly is an aluminum skin, I think I would cut strategic holes in the underbelly and patch accordingly.

It's a woven fabric type. Not sure exactly what it is made out of. The insulation sits on top of the underbelly material. Looks a lot like in this picture -

 

[Jeff H Young]

I would consider running the main to the water heater location exposed in a conduit insulated perhaps pop through floor in w/h closet usually its mainly accessible from the w/h to both bath rooms easily from topside often the kitchen is run underneath 15, 20 foot away. I don't run PEX much but rats supposedly like to gnaw at it and freeze protection could be issue that's why I mentioned inside a conduit insulated .
So what I was getting at my limited amount of mobile home work only had 2 places coming through floor 1 at the water heater 2 at kitchen sink maybe you have straight stops under floor for toilets just gotta scope it out

 

[dieselfuelonly]

I spent quite a bit of time under the house today levelling up some of the piers and took a good look at what would be involved in cutting through the underbelly/insulation and doing the plumbing from below. Since the underbelly wrap is in good shape I really hate to tear it up. I think I will probably end up doing things from the top - if I plan it out right I'm hoping I can get by with cutting (only a few, I hope) holes in the floor. I think the time spent replacing a few linoleum tiles and a piece of linoleum in the kitchen and in the bathrooms would be better than chopping up the underbelly and insulation and having to try to re-seal it hoping it holds. I think I'll have to cut one access hole in the common bathroom that I should be able to fish the PEX through from the attached garage. I will probably have to add some access panels for the tub/shower in the wall of the adjoining room. From there, I guess the next hole would be in the kitchen, and lastly one in the master bathroom. I already have access through panels in the laundry room to the shower/tub faucets. Moving the water heater out of the master bedroom closet and into the garage removes a fair amount of complication too. Will post up the results of whatever I end up doing.

 

[Tuttles Revenge]

I agree with not wanting to cut up the underbelly fabric. My GF's tiny house we built had galvanizied sheet steel as the underbelly.

Could you remove a bathroom vanity in order to keep the floor hole in an unfinished location?

Good that you're planning ahead this much too. I've worked on a few repipes where that amount of pre planning made the job go so much better and faster.

 

[dieselfuelonly]

I agree with not wanting to cut up the underbelly fabric. My GF's tiny house we built had galvanizied sheet steel as the underbelly.

Could you remove a bathroom vanity in order to keep the floor hole in an unfinished location?

Good that you're planning ahead this much too. I've worked on a few repipes where that amount of pre planning made the job go so much better and faster.

Removing the vanity would be an option, but honestly with the time spent doing that I can just as easily lay another piece of vinyl in the floor.

I cut a hole in the middle of the floor in the common bathroom next to the duct and ended up in the right spot - right above the trough of the underbelly where the old poly-b pipe was run. I was able to run a fish tape up there with the help of an old piece of unused wire that was sitting right there, and then pull 2 pieces of 3/4" PEX from the bathroom over to the attached garage where the water heater and main water connection will be relocated. Eventually managed to get 2 pieces of 1/2" PEX ran from the vanity down to the same hole where I can tee off the 3/4". Still need to run a piece of 1/2" for the toilet and cut out some drywall so I can access the shower/tub spigot and pull that pipe. But I figured that would be the easiest so I saved it for last.

I went ahead and cut an exploratory hole next to the duct in the kitchen the same distance from the wall as I did the bathroom. My same wires I used to help pull the fish tape through were there, however I didn't have any luck getting it through - the wire was loosely hung to the joists and no matter how much I tried the fish tape would get jammed up. Then I realized it wouldn't do me any good as there is no way I would be able to pull the PEX back through those straps that the wire was hung by.

Looking at the distance I have to go from the hole in the bathroom to the hole in the kitchen, I honestly don't see an easy way of getting the PEX pulled through there. Especially with the PEX being coiled, even if I try my best to straighten it out I don't think it is going to go easily. Straight sections might help, but then I'm stuck with coupling a bunch of them together and I still see them jamming against the insulation and getting stuck trying to push them through. Fish tape doesn't make it far and just gets jammed up in the insulation that lays on top of the underbelly. At the other end of the house things get a bit more spread out with the kitchen sink, ice maker, dryer, and the master bath which has a double vanity in a hallway that connects to the toilet/tub in their own room. That will only make it more difficult to work from above.

Looks like I may just have the cut the underbelly after all. Hate to do it, but it seems to be the most realistic option at this point. If I was redoing all the plywood on the floors it would be another story and easy to do from the top, but that's all in good shape. I guess the one advantage of doing that is I can secure the PEX every other joist like its supposed to be done, and branching off to everywhere it needs to go should be all right there and accessible. How I will re-secure the underbelly I don't know yet, as it's the kind that is layed down above the metal beams before the rest of the house is built. Will have to cut some out tomorrow and find out.

 

[Tuttles Revenge]

There are threaded rods used to fish wire. That may help get further. They usually come in 6ft lenghts.

 

[dieselfuelonly]

There are threaded rods used to fish wire. That may help get further. They usually come in 6ft lenghts.

I ended up cutting the underbelly right up against the metal frame rail from one end to the other. Rolled up it against the duct and tore out the parts that were already hanging loose and not doing anything. Sucks that I had to do that, but honestly there's no reasonable way I would have been able to replumb this house without doing it, especially once I got to the other end of the house where the water lines for the master bath/double vanity in the connecting hall/laundry room were. It was either that or have 10 holes cut in the floor to try to snake all the plumbing around from above.

Got my 3/4" PEX run from one end to the other and most of the 1/2" runs done minus the laundry room and the shower in the common bathroom. What a nightmare that was. Now I just need to connect them to their various faucets, etc.

Since there isn't really any way to pull the underbelly back tight all the way to the frame rail and re-secure it, I think what I will do is put some insulation up from the edge of the frame rail towards the side of the underbelly that is still attached. Probably a foot or two. Then pull the underbelly back towards the frame rail as tight as I can and staple it back up, overlapping the insulation I'll put up between the joists.

That will at least get me insulated enough to keep pipes from freezing until some more mild weather in the spring. Then I will probably have to address the whole insulation issue more. I've noticed the ducts aren't completely wrapped and sweat quite a bit. I'm sure this has been dripping on the underbelly insulation for a long time especially during the summer.

I need to replace the plastic above the dirt floor, what is there is in rough shape and not doing much to prevent moisture from coming up.

It's very tempting to remove all of the underbelly and insulation up against the bottom of the house completely. Then build a 2x4 frame skirt that wraps all the way around the house and insulate that instead. Wrap just the ducts to keep them from sweating, and put some vents in the 2x4 walls to allow for some circulation. New 6-mil plastic on the bottom side and bring the grade up around the outside of the house some and I think it would stay pretty dry.

Guess I need to find a forum geared more towards manufactured homes to answer that, I realize this is a plumbing one!

 

[Reach4]

Could you get some heavy duty plastic, and attach that to the underside? It looks like they used some furring strips to hold the middle. You could wrap the edge of the plastic around furring strips, and then screw the furring strips into whatever is above maybe.

House wrap might be another material to consider, but I tend to think the heavy plastic (not permeable) would be good for your warm area.

 

[Tuttles Revenge]

boxing in the entire perimeter is going to be huge for insulation value, its keeping that air from moving / transfering heat is a big plus. Insulating the bottom too will be key.