Grey Water Tank Problem

[kycamper]

After a three week long trip, I have an unusual problem that I would like "to throw out there". I can run water in my kitchen sink ( 21RBS ) until it won't drain anymore and leave it full, then fill the bath sink with open drain and it will not drain either. The sensor says the thank is only 1/3 full, and I am certain that it is only partially full. I believe that I have a venting issue somewhere, i.e. at the bath sink, up on the roof, at the tank ( is there a vent on the tank???). I just got back today, but I intend to pour one gallon at a time into the kitchen sink, with a completely empty tank, and count how many gallons it takes before it won't drain. Then I will bring it to be repaired. Any ideas why this is happening. If I am camping without sewer hook up, this could get real old real quick. Thanks for any ideas.

[hdrehder]

I've suspected a similar issue - grey tank acting full - but have not done the measuring test yet. Had no idea what to attribute it to...  Interested in hearing more about your tests.

[daplumbr]

I think (no direct experience) that each sink has an air admittance valve and that the grey tank has a roof vent. If neither sink drains properly after just a few gallons, I would suspect a roof vent problem.

[tinkeringtechie]

Chances are that the vent pipe was pushed too deeply into your tank. Once the water reaches the vent pipe nothing new  will enter the tank. You could probably rent one of those inspection cameras and go up the dump valve to verify. Not sure how you'd fix it though...

[charliem]

[font size="3"]I had the same problem and also thought of the vent pipe pushed too deeply into the gray tank. I could cause the burping of the sink drains while dumping 5 gal jugs into the shower. After much discussion with LL I took the rig to CW for service. They replaced the AAV in the bathroom and re-ran my test. Problem fixed. I don't understand how that AAV was causing the problem, but the CW techs had apparently seen this before. Maybe I don't fully understand the operation of the AAV. The gray tank vent is connected very close to the shower P-trap so pushing a lot of water down the shower drain could back up into and block the vent pipe. My problem also occurred at about 1/2 full.

Again, I don't quite understand why the problem was occurring or why the AAV might have been causing it, but it seems to be fixed. I verified by dumping "calaibrated" water jugs down the drains.  Since then, on camping trips, I am able to use the shower, bath, and kitchen sinks with no problems until the the gray tank shows full on the SeeLevel gauge. Using the "calibrated" jug measurement I was able to put 33 gallons into a freshly emptied gray tank before backing up into the shower with no burping.
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[kycamper]

Once again, charliem, you are my hero. I will make an appointment with CW asap, and report back. 
Thanks

[charliem]

[font size="3"]Check with Don at LL before you set up with CW. LL covered mine under the one year warranty.
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[kycamper]

i had discussed this with Don. He indicated it would be under warranty. Can't imagine that it would not be covered. I also had false reading with my black tank sensor from day one. It read "full" when it was completely empty and brand new!! Don sent me a diagram of the wiring and suggested that the ground wire was too close to the sensors. I will mention this to CW also, as it would be nice it the sensors worked.

[jerrybeaird]

Hi gleamb,

After reading your post, it seems to me that I have the same problem with our new 21 RBS, although I am out of town and cannot verify by actually doing the "Gallon jug" thing.  Can you let us know the resolution after CW fixes it?
Thanks!

[jtelles3993]

Another 21RBS owner here, I'll run a gallon check in my grey tank as soon as it's safe to water up.

[kycamper]

Just got done with my test. After 10 gallons down the kitchen sink, the panel read 1/3 full and there was loud "gurgling" coming from the bathroom sink. At 20 gallons, the panel read full. At 23 gallons the kitchen and bathroom stopped draining. There is clearly a " venting issue " here. I just don't know if CW will attempt a fix . I will call them tomorrow and find out. My black tank reads " full " and it is empty. Did it from the day I picked it up from my dealer. Brand new. Don, at Livinlite suggested that the ground was " too close " to the sensors and, thus, was giving a "false positive ". My wiring seems to be covered with a foam type spay on insulation. Again, I wonder if CW can fix it.

[charliem]

[font size="3"]Re the OEM sensor panel:

Originally LL did not supply any tank monitoring system. Several of us were disappointed, but not a deal breaker. TinkeringTechie and I installed the SeeLevel 709 system and are very satisfied. The SeeLevel sensors are affixed to the exterior of the tanks, thereby eliminating the failures found with the probe system. A few more bucks, but they really work. Recently LL has been supplying an inexpensive probe monitor system. These are characterized by four probes penetrating each tank. In theory they sense the physical level of the tank fluid by change of resistance and light the corresponding number of lights on a panel. It don't work that way. The real world allows crud to build up on the probes leading to false high readings. This occurs from normal filling, but also results from incomplete cleaning, road sloshing, repeated filling and draining. So the general conclusion from users is 1) sorta works on the fresh tank, 2) marginally effective on gray tank but you never can rely on it and 3) totally useless on the black tank.

The remaining function is the battery "measurement" function. This is simply a measurement of the battery voltage ( measured somewhere?) that leads to a 1 to 4 light display estimating battery SOC. After lots of research the true story is out. The top light means nothing more than the battery is being charged. It does not mean full charge. The bottom light means you totally forgot to bring the battery. If you ever had a real battey show one light you should be headed to the battery store next. The other two lights are in between somewhere.

So the conclusion of all the know and most that just have experience is: the probe monitor is sorta useful for the fresh water tank, but not much else. BTW this 4 probe/ 4 light system is found in 99.9?% of all low, medium, and even high end RVs.


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[charliem]

[quote source="/post/7412/thread" timestamp="1425415287" author="@gleamb"]Just got done with my test. After 10 gallons down the kitchen sink, the panel read 1/3 full and there was loud "gurgling" coming from the bathroom sink. At 20 gallons, the panel read full. At 23 gallons the kitchen and bathroom stopped draining. There is clearly a " venting issue " here. I just don't know if CW will attempt a fix . I will call them tomorrow and find out. My black tank reads " full " and it is empty. Did it from the day I picked it up from my dealer. Brand new. Don, at Livinlite suggested that the ground was " too close " to the sensors and, thus, was giving a "false positive ". My wiring seems to be covered with a foam type spay on insulation. Again, I wonder if CW can fix it.[/quote][font size="3"]Gleamb,[/font]

[font size="3"]I'll be very interested in you results and outcome with CW. On the gauge system see my dissertation above.  Record you results and they may give you some useful indications on the road. As I said before I don't understand how my CW work fixed the burping problem, but it seems have. I suppose I could run more tests, but that gets old after a while. Didn't I spend all this money to go camping? I've got my own separate lab in the garage.

Camp On 8-)
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[jerrybeaird]

Well I just came back from a cold trip to Boston and I was able to do the "gallon" test tonight.  Just as I suspected, filling the kitchen sink, at gallon 14, the bathroom sink stated gurgling. By the gallon 15, both sinks stopped draining.  Rats!... Is it just the AAV at the bathroom sink?  I know that they are inexpensive.  Do they just screw on with Teflon tape?

I hate to drive it to CW for a warranty repair that I could just fix it myself.  Any help or insight would be appreciated.

Thanks!

On a side note, the tank read 1/3 full at ten gallons and read 2/3 on gallon 15 when it stopped draining.

[charliem]

[font size="3"]nd1979: This will be a very wordy answer to your question. Please read to the end.

By my count we now have four confirmed instances of this problem (gleamb, CMac, nd1979, and charliem). The problem is apparent improper gray tank venting which manifests as lack of draining and/or gurgling and blowback from sink drains when the tank is known to be only 1/3 to 1/2 full. This is different from and independent of the inaccurate gauge reading issue. This post will discuss only the apparent vent problem.

The gray tank is vented to the roof by a pipe inserted into the tank close to the shower drain. The shower drains via its own P-trap into this same vent pipe above the level of the tank top. Plumbers call this a "wet" vent The two ( one for BHS) sinks drain through a second pipe into the tank via a second tank penetration. Each sink has a P-trap and an Air Admittance Valve (AAV). The AAVs allow air to enter the drain pipe downstream from the P-traps so the P-traps are not sucked dry. The AAVs should not allow air and gasses from the tank to escape into the camper. In other words, the AAV is a one way air valve, allowing air into the pipe/tank, but not out of the tank. The AAV does not vent the tank.
As detailed in my previous post, I originally thought the problem was the vent pipe shoved too far into the tank, thereby blocking the flow of air when the tank level reached the bottom of the vent pipe. When air trapped in the tank cannot be released through the vent stack it will be forced back up the sink drain pipe, thereby building up pressure in the sink drain pipe. If the AAVs are working as I understand them, the only exit for this air is back through a sink P-trap, thereby causing gurgling and water splatter from the sink drains.

I verified the roof vent pipe was clear of obstruction and coordinated a warranty repair with Don at LL. I took the camper to CW for the work. The techs there seemed familiar with the problem. They confirmed my problem by emptying 5 gallon buckets into the shower and observing the gurgle/splash from the sinks. They "fixed"  it by replacing the AAV under the bathroom sink and reran the bucket test. Problem fixed! (?)  

This never did agree with my understanding of the physics of the system. Replacing the AAV should not have fixed a venting problem. However CW claimed they had seen this problem before and it was just a faulty AAV. The sink drains and the shower all work properly now and a full tank backs up into the shower (lowest drain) as expected. That said, if the  "new" AAV was allowing air to escape back into the camper the observed results would be the same. However, this would also allow gasses from the tank or a CG sewer to leak back into the camper. Bad thing. TinkeringTechie has suggested a test to confirm or deny this using a leaf blower, but I have not yet been able to do this (something to do with a total knee replacement).
 
All of this is a long way of answering nd1979's question. The AAVs just screw into a coupling on the drain pipe next to the P-trap under the counter. If I understand what's happening you should be able to "fix" your problem by completely removing the AAV, leaving an open pipe. NOTE: This is not a permanent fix since it allows tank/sewer odors to back up into the trailer. If the gallon jug test then passes it will further confirm our suspicion that the primary vent pipe is pushed too far into the tank. Dropping the tank and fixing that defect is beyond what we as new owners should want to tackle. If  all four of us can get together in our approach to LL, maybe we can get a resolution and help LL avoid future occurrences. I'll volunteer to call Don if you guys can feed me your observations, tests, and results. [/font]