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  • Black Tank: How to tell when it is really full.

    My blank tank level lights lie. I dump and saniflush and even stick a water wand down the biffy and spray. Still... when empty it says 3 dots. A day or two later it says 4 dots.

    Is there a secondary way to tell when the black tank is full? From reading on here I think I remember a check valve that would make the nasty stuff climb the vent pipe instead of the toilet pipe. Is that right? With the grey tanks I can know they are full when water stands in the sink or shower. Is there a reliable secondary indication that will verify that the blank is really full? I'm dumping that tank at four dots and the quantity that exits is nowhere near a full tank.

    Thanks
    steve
    Steve and Shelley. Minnesota
    2017 RAM 3500 LLH CC 4x4 LB DRW 6.7ctd Aisin 4.10 Air Level aka Shrek
    2018 AF 27-5L, HW50C ems, Maxxis Tires, TST 507, dual AC, tank heaters, Rear Camera, Toppers, 640w Solar, Victron MP 3000 Inverter, MPPT 150/85 solar charge controller, CCGX Color Monitor,BMV702 Battery Monitor
    , 440AH Lifeline AGM, aka Fiona

  • #2
    The toilet drain line in my 25Y is a straight drop into the black tank. A simple, but not pleasant, and sure fire way to see if the tank is truly full is to turn off the water supply, hold the flush valve open, and shine a flashlight down into the tank.

    I don’t know if this method will work on your 27-5L.
    Jim and Esther

    2005 Chevy Silverado LS 2500 HD, Duramax/Allison, extended cab, 8-foot bed, 3.73 posi-traction, AirLift air springs, EezTire T515/SP TPMS, fog lamps, alloy rims, Kenwood stereo

    2016 Arctic Fox 25Y, slide out topper, 15k air conditioner, powered scissor jacks, thermal pane windows, swivel rocker/recliners, 300w solar panels, 6v batteries, Blue Ox SwayPro 1500, Progressive Industries EMS-HW30, Giandel 2200 watt pure sine wave inverter

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    • #3
      Many of us have the same problem. I decided to find out how much our black tank will hold by filling it with fresh water and watching the level by peering into the toilet. I filled our tank with the Sani-Flush system but a water hose into the toilet works just as well. I was surprised how slowly the water rose in the toilet's drain pipe. Apparently the pipe extends well below the top of the tank. So now I have a good visual reference and "full" occurs long after all the lights are on.

      Friendly Bob
      Bob and Nancy
      ======
      Proud former owners of a 2011 Arctic Fox 25R (2010-2013) and an Arctic Fox 22G from (2001-2010). Current happy owners of Northwood cross-town cousin.
      ---------
      2010 Dodge 3500 Laramie Crew Cab SWB, Cummins, 4X4, Snugtop, 1,200#/12,000# Equal-i-zer.
      Retired: "Twice the husband, half the money"

      Comment


      • #4
        My 27-5 has a bend - can't see the content level looking down. Also - I'm a weekender so haven't been totally full yet - - but it may be good ole eyesight is the right way. In mine, if the sludge got up to where I could see it (IE: above the bend) I would still have enough capacity for a few more uses before the toilet valve wouldn't close.

        Dunno if that helps?

        -Kyle
        2018 Arctic Fox 27-5L
        • 4 pt Auto Level / 15k Single AC / 50 Amp (no Gen)
        • 3xFantastic Fans / 3xFantastic Covers
        • Sofa with Air Bed / Dinette / Slow Rise Shades
        • Factory 2" Receiver hitch
        • MODS
          • 195W Solar / Rear Camera / TPS / Flagpole Buddy / BMV-712
        2015 Chevy 3500 Dually LTZ
        • Duramax / B&W Turnover w/Companion / 40 Gal transfer tank.

        Comment


        • #5
          Our very first night in our 27-5L we stayed in a full hookup park, and I filled the fresh tank, then stood on the toilet pedal until I could see water in the tube. About the same time, the pump started getting some air. Then I dumped it the black tank, refilled the fresh tank and turned on the shower and bathroom sink. Same results, the pump started getting air when we had water no longer draining in the shower.

          So, figuring our normal useage, I don't have to worry about tank capacities until we have used two fresh tanks, and we learned that on our first night. Now all I use the monitor for is to see how much fresh water we have left.
          2018 27-5L 4 point leveling, 30 amp, 320 watts of solar.
          2000 F250
          2000 27-5L sold after 8 great years.

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          • #6
            On our 27-5L the pipe is not straight so you can not look down to check levels. We do boondocking most of the time and the indicator lights also say 3-4 lights just after I dump. I usually rinse several times as well as use soap and other methods to try and get the lights to be more accurate. So here is how I calculate the black tank level. I believe on our rig the black tank is 65 gallons. So with simple math, if we boon dock for 7 days and estimate a huge 5 gallons a day (I can see what some of you will say) that is only 35 gallons. So as silly as this may sound, most of us do not waste 5 gallons a day, including flushing water. In a week that is only 35 gallons. So using simple math we have gone 15 days and did not have a problem. I can hear some you now that know me saying, "Oh Kirk, your more full of it than just 5 gallons!"

            Kirk n Kay and Mickey, the big black lab
            2012 F-250
            2016 27-5L

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            • #7
              My lights don't work either. I quit worrying about that several RVs ago. We run out of water before we run out of black and gray capacity. If you need a secondary method, When you step on the pedal and nothing goes away, you are full. Another way to fill your tank is to dump, saniflush, dump again and plan to turn off the saniflush and dump again in 5 minutes. The water running off the roof is not condensate from the A/C. Do not step on the pedal to see what happens. Senior moments.
              Ken and Rita Madsen
              2018 GMC 3500 Duramax, 2016 27-5L

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              • #8
                My 27-5L has the bend so I can't look straight down. If I understand what everybody is saying then as long as I can't see it coming round the bend, and my toilet still flushes it down ok... then I'm not full. Somehow I thought there was some check valve down there or something.
                Steve and Shelley. Minnesota
                2017 RAM 3500 LLH CC 4x4 LB DRW 6.7ctd Aisin 4.10 Air Level aka Shrek
                2018 AF 27-5L, HW50C ems, Maxxis Tires, TST 507, dual AC, tank heaters, Rear Camera, Toppers, 640w Solar, Victron MP 3000 Inverter, MPPT 150/85 solar charge controller, CCGX Color Monitor,BMV702 Battery Monitor
                , 440AH Lifeline AGM, aka Fiona

                Comment


                • #9
                  Our black tank has yet to be a problem. Longest has been about 14 days and no sign of a problem. But the shower and bath sink gray tank has been problematic. I am thinking it may be the roof vent plugged but I still have not investigated it. Retirement is not for the time challenged. Anyway, we have had two times where an eruption of gray water comes up through the sink drain while using the shower. If it were just a full tank I would expect the shower to back up first. So the picture in my mind says the drain pipe from the sink may be too low and hits the water level before the tank is full. But the question is, if that is true why does it not vent to the roof and not blow out into the bathroom. I have removed the vacuum brake for the sink drain and it looks clean.
                  Boondocking is all fun and games until the sink drain blows. Anyone else had this? I tend to not let it get too full these days.
                  Peter and Fran
                  2016 AF 27-5L
                  , 50AMP, 4pt leveling, 10 Cu Ft Refrigerator, 15K AC + bedroom AC, Onan 5.5 generator, Progressive Dynamics EMSHW50C, Slide Toppers, TST 507 flow through with repeater, Cadet digital AC heater, 52" ceiling fan LED light, Dirt Devil CV1500 Central Vacuum, water filter system, 480 watt solar charger, 440 AH AGM battery bank, Magnum MS2012 2000 Watt Pure Sine Wave Inverter/charger, TorkLift steps, SRE4000, 17.5" Alcoa rims, 7k axles


                  2017 F-450 Super Duty, B&W Companion

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                  • #10
                    We've not had the erupting sink drain adventure yet. All we get is the water filling up in the shower basin if our tank is full. I am at a loss to explain how the sink can spew water with its level being above the shower if tank level was the culprit. It seems like your holding tank might be getting pressurized somehow. Does it happen both on the water pump and city water feeding the shower?
                    Steve and Shelley. Minnesota
                    2017 RAM 3500 LLH CC 4x4 LB DRW 6.7ctd Aisin 4.10 Air Level aka Shrek
                    2018 AF 27-5L, HW50C ems, Maxxis Tires, TST 507, dual AC, tank heaters, Rear Camera, Toppers, 640w Solar, Victron MP 3000 Inverter, MPPT 150/85 solar charge controller, CCGX Color Monitor,BMV702 Battery Monitor
                    , 440AH Lifeline AGM, aka Fiona

                    Comment


                    • #11
                      Originally posted by Fox will Travel View Post
                      ...

                      But the shower and bath sink gray tank has been problematic....

                      Anyway, we have had two times where an eruption of gray water comes up through the sink drain while using the shower....

                      Anyone else had this?

                      ...
                      We have exactly the same symptom when our gray tank is full - it backs up into the sink before the shower pan fills. So, we know when the sink burbs it's time to equalize the gray tanks.

                      Bill
                      Bill, Mary, and Scottie
                      2015 RAM 3500 Crew Cab, Long Bed, 6.7 Cummins/Aisin, SRW, Hensley BD-3 Hitch
                      2017 AF 27-5L
                      http://badges.fuelly.com/images/smallsig-us/719790.png

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                      • #12
                        Back to the original question: How can you tell when the black tank is getting full.

                        You need to listen to your toilet. As the drop tube fills with "water" the tube traps air and you will actually hear it burb. At first it's very slight but it gets more pronounced as you continue to add more "water".

                        The black holding tank on the newer AF27-5L is huge - I think it's 65 gallons on our 2017.

                        We have only once filled the black tank on this trailer. Now remember we typically add a lot of water to the black tank after we dump so I'm guess we start with 5-10 gallons of water before we ever use the toilet.

                        Listen to your toilet!

                        Bill
                        Bill, Mary, and Scottie
                        2015 RAM 3500 Crew Cab, Long Bed, 6.7 Cummins/Aisin, SRW, Hensley BD-3 Hitch
                        2017 AF 27-5L
                        http://badges.fuelly.com/images/smallsig-us/719790.png

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                        • #13
                          I've used dishwasher tablets for many years. They work well. However occasionally I would get false indications. My solution was to dump a significant quantity of ice in a empty tank and go for a drive. Hasn't failed me yet.

                          Woods
                          07 Fox 31WRB, Aria, AGMs, RPowerTwins, Heatpumps, Maxxfans, Sur eflow 57, 50amp, dualpane, Reese nocam trunnion, more.
                          04 6.0L 4X4 Excursion. AirLifts, Vair, ARC, XCal3, EGRfix, 4A pillar Cobalts, AFE, MBRP, Hadley, Bilsteins, Brakesmart, Colorado's Monarch Pass Avatar

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                          • #14
                            Originally posted by BZawlocki View Post
                            Back to the original question: How can you tell when the black tank is getting full.

                            You need to listen to your toilet. As the drop tube fills with "water" the tube traps air and you will actually hear it burb. At first it's very slight but it gets more pronounced as you continue to add more "water".

                            The black holding tank on the newer AF27-5L is huge - I think it's 65 gallons on our 2017.

                            We have only once filled the black tank on this trailer. Now remember we typically add a lot of water to the black tank after we dump so I'm guess we start with 5-10 gallons of water before we ever use the toilet.

                            Listen to your toilet!

                            Bill
                            X2
                            Kim + Betsy
                            I do all my own stunts....just ask my wife.
                            2017 AF 35-5Z
                            2017 F450 Lariat

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                            • #15
                              Originally posted by BZawlocki View Post
                              Listen to your toilet!
                              Well I told DW to listen to the toilet and got an eye roll. Now she is calling me the toilet whisperer.

                              Steve and Shelley. Minnesota
                              2017 RAM 3500 LLH CC 4x4 LB DRW 6.7ctd Aisin 4.10 Air Level aka Shrek
                              2018 AF 27-5L, HW50C ems, Maxxis Tires, TST 507, dual AC, tank heaters, Rear Camera, Toppers, 640w Solar, Victron MP 3000 Inverter, MPPT 150/85 solar charge controller, CCGX Color Monitor,BMV702 Battery Monitor
                              , 440AH Lifeline AGM, aka Fiona

                              Comment

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