Seeking Advice on Hidden Leak in 2004 Pace Arrow 35G

[Gargohere]

Hey everyone,

First time posting here, but I wanted to reach out to the community for some insight and suggestions.

I picked up an ’04 Pace Arrow 35G earlier this spring. It had been sitting unwinterized for an unknown period, parked nose down on a steep hill. When I first turned on the water pump, it was shot and several fittings were leaking, including one behind the shower and a few in the sewer hold area. I replaced the pump and repaired the leaks promptly, and everything seemed fine.

However, I noticed that the shower would back up during use and the kitchen sink would gurgle. Cleaning the drain and vent didn’t help much, so I chalked it up to poor design. After our last trip, I discovered the bathroom floor was squishy especially near the sink. I removed every access panel I could and ran a generous amount of water through the sink and shower to check for leaks. Everything inside appeared bone dry. This RV has a washer/dryer which sits to the left in "floor squish.jpg" I checked behind and I can't find any water either. However that floor is a little messed up there as well.

Over the next few days a friend used the RV and the floor got progressively worse. I finally cut the linoleum under the bathroom sink and found the subfloor completely soaked. (Pulls hair emoji)

Based on what I’ve seen, I’m fairly confident the leak is somewhere between the grey water tank and the shared vent/drain pipe for the sink and shower. Unfortunately, accessing this area seems nearly impossible. There’s no side access from the RV exterior, and nothing accessible from inside without pulling cabinetry and cutting into the floor.


When I shine a light down the crawl space from the front of the RV, I can see the grey and black tanks, but it's moot since I can't actually see any water pipes going into the tank. Not to mention it seems dry.

Check out the attached photos and floor plan.

So I’m looking for advice:

• Has anyone dealt with a similar issue?
• What did you find, and how did you approach the repair?
• Are there any plumbing diagrams or resources you’d recommend?
• Surely someone's got photos?

The manuals I’ve found are as expected pretty generic and not much help.


Thanks in advance for any guidance!

 

[gwinger]

Sounds like lines were frozen at least one time and in many places.
Some of the drain lines may have also frozen and cracked in hard to reach places.

 

[Kirk]

However, I noticed that the shower would back up during use and the kitchen sink would gurgle. Cleaning the drain and vent didn’t help much, so I chalked it up to poor design.

I very much doubt that your drain problem is from the design. When you add that to the indications of a leak. I suspect that the two are related.

Based on what I’ve seen, I’m fairly confident the leak is somewhere between the grey water tank and the shared vent/drain pipe for the sink and shower.

The other thing to consider is if the leak is from the water supply or from the drain, or possibly both. An easy way to check for a supply leak is to put water into the potable water tank and turn on the pump. It should run until you get water through all of the lines and then stop running if the faucets are all closed and it should not run again for at least an hour or more. If the pump starts again over and over, that indicates that you have a leak in one of the water lines. In general, water that leaks slowly works downhill and not up so the wet floors must be getting water from a source at or above the floor level.

 

[gwinger]

The kitchen sink and shower may be two different problems.
Check under the sink for an air admittance valve. If it is stuck, it will make the draining water gurgle.
It sounds like you have more than one problem though.

 

[Gary RV_Wizard]

Sound advice from Kirk & gwinger. The water system in those coaches are pretty much a standard design. It has some limitations in drain pipe down-angle and venting due to being in an RV, but generally they work adequately. Drain lines don't typically suffer freeze damage, but that nose-down attitude could have trapped waste water in atypical places.

All the plumbing is in place before the coach floor and body goes on, so repair is problematic. Nothing to do except tear up the floor to get at it. Sounds like you have a rotten subfloor to replace anyway, so may as well dig in.

 

[Gargohere]

@gwinger
Agreed on the freezing for sure! It appears both sinks have an air admittance valve. Correct me if I’m wrong but the gray water roof vent is where the air exits and these admittance valves allow air to go with the water as it flows down. My trouble is with air exiting through the kitchen sink...



@Kirk
To clarify on the gurgling, the shower/bathroom sink share the same pipe as the vent to the roof. It appears that water hangs out and prevents the gray water tank from venting as it fills. Since there’s a buildup of pressure it comes out at the easiest alternative location. It’s super probable that this pressure is amplifying the leak that already exists. (I wonder if something is stuck in there…)



I found the lines behind the water heater to be leaking. I fixed them yesterday. To test I enabled the water pump and before I left for the night, I turned it off but left the lines pressurized. This afternoon I turned on the faucet and it appears that the system retained most of the pumps original pressure. If there is a leak on the supply water side, it is likely minimal. I’ll find a pressure gauge to double verify in the coming days.



@Gary
Agreed. It was on the market for a while and a few folks came and tested the water before last winter. It is totally likely water got trapped as stated.


Photos...
So at this point it seems likely I will need to cut. I’m hoping someone has photos taken during a remodel to help map out the locations of the tanks and plumbing. It would be so helpful to not go in completely blind!

I'll post updates as they come, though it may be a little while before I get the balls to cut the floor

 

[gwinger]

The admittance valve at the kitchen sink may be stuck closed. The valve is closed until water runs. That would explain the gurgling.
The roof vent is there to vent air when the tank is filling.
In a sticks and bricks house, most drains are vented to the roof through a common pipe. Hard to do in an RV.

 

[Kirk]

My trouble is with air exiting through the kitchen sink...

The purpose of the admittance valve is to prevent the water exiting the sink from drawing a vacuum in the lines and thus making it slow to drain. What you described is exactly the symptom of on that is stuck shut. It is closed to air exiting from the tank to prevent the odors of waste water from entering the RV.

If there is a leak on the supply water side, it is likely minimal

By far the best way to leak check an RV water system it to leave the pump on while you are in the RV and listen for it to run from time to time with no water being used. The pump is not difficult to hear, and it takes very little loss of water to make it run for a few seconds.

 

[garyb1st]

We also have a Pace Arrow 35G. Ours is an '05 but there's not much different in layout. We've had it for about 8 years and the only leak I ever had was from the shower. Thought it was a pipe issue. Turned out to be the fittings that the shower head attaches to. Opened it up, tightened it and no more leak. Had a slow shower drain for a while. Don't recall what the issue was but it was not major. Maybe some hair or whatever that didn't drain fully. Also the spray hose of the toilet can leak. The fix is a new spray hose or possibly just tape and tightening the connections. The bowl can also leak. I've replaced the seal which solved the problem. Only used the washer/dryer one or two times but never had a leak. If possible talk to the previous owner and ask about leaks.