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Thread: Serious Plumbing Considerations

  1. #11
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    Debi,

    This is an issue that is not hard to visualize. If you have a HeadHunter type toilet with the associated flush valve picture in your mind a toilet bowl with water in it. The water in the bowl is in direct contact with the waste line going to the black water holding tank, and it is also in direct contact with the fresh water used for the flush cycle.

    What separates that toilet bowl water from the fresh water holding tank is the flush valve that under almost all circumstances seals so tight, it shuts off fresh water that is under pressure from leaking past the valve. That seal also prevents any water in the toilet from backflowing into the holding tank.

    It is only when the flush valve fails to seal, or shut off the flow, that problems occur. In any coach in which the flush valve has functioned properly it is unlikely the fresh water holding tank has been soiled. In fact, in some cases the converter has taken steps which prevent the contamination of the fresh water holding tank by installing a check valve between the pump and the flush valve, thus making contamination even more unlikely.

    When we started "camping" in our first coach our concerns were like yours and we just decided to never ingest water from our holding tank, instead preferring to use bottled water. Even when I modify our plumbing system to almost completely eliminate cross contamination we are unlikely to change our practices.

    In the context of the toilets and valves discussed above an air gap is not possible. It would require the valve to be mounted above the toilet, and to allow the water to flow into the toilet from above the water flood level. The way the toilet is designed it requires the high volume flow into the waste line below the bowl to create a very low pressure area to "vacuum" out the contents of the bowl. It is a very effective design, but like I said originally, it is a compromise.

  2. #12
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    [QUOTE=Jon Wehrenberg;10135]Debi,

    This is an issue that is not hard to visualize. If you have a HeadHunter type toilet with the associated flush valve picture in your mind a toilet bowl with water in it. /QUOTE]

    Jon, thank you very much for the additional explanation. I understand perfectly now. Like you and Di, Bob and I will likely continue with our bottled water routine

  3. #13
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    Now I know why I'm real happy to have an electric toilet!

  4. #14
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    I never drink the water. Jim, I would spend beaucoup bucks + the cost of a case of Ozarka water and never look back.

  5. #15
    Just Plain Jeff Guest

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    Jon: As I recall, you had briefly mentioned something about the toilet issues at Titusville. Thanks for remembering to bring the matter up here for all to share.

    You had also commented on the temperature rise whilst using the factory-supplied exhaust retarder. We both apparently have the same system, with the right steering column range adjuster.

    Just for the heck of it, I took the bus out the other day and watched the temperature rise, and indeed it does. However, the rather fascinating thing is that as quickly as the engine oil temperature rises, it cools just as fast. Now that seems like a puzzlement. One would think that if oil temperature can rise that quickly, how in the world would it cool down equally as fast? Logic says that could be due to one of two things: Either the engine oil cooler design is an incredibly efficient and effective system, or that the apparent temperature rise is an artifact created by the use of the retarder, which clears as quickly as it appears?

    Of course, this has nothing to do with toilet water, but it was part of the conversation we had at the same time, so, what the heck.

  6. #16
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    JPJ,

    It was posted somewhere else about how the retarder works. I learned the temperature sensor is located at the outlet of the transmission retarder. The reason the temperature changes are so dramatic is because the sensor is measuring the fluid temperature at the point the retarder affects the temperature, so if the retarder is functioning it translates that work into heat that is measured as the heated fluid leaves the retarder. As soon as the retarder is no longer in use (such as when you step on the gas or turn off the retarder) the fluid passing through the retarder and past the sensor has not absorbed any additional heat. It does not necessarily mean the transmission fluid intercooler is efficient.

  7. #17
    Just Plain Jeff Guest

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    OK, so if that is the case, what is happening here is that a 'sample' of the overall oil is rising in temperature during operation of the retarder and then when the retarder is 'disengaged,' the sample is released (dumb way of saying it, but you get it) back into the overall oil flow, so the apparent oil temperature decreases?

    If that is the case, then it's no big deal? Oil certainly can be be as hot as 220F without destroying its lubricity.

  8. #18
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    You cannot make a statement like that to apply universally.

    High temperature is the enemy of our fluids. If you never expose the fluid to a temperature of (insert your own value here) it is possible the life of the fluid will not be shortened. However, the use of a retarder on our coaches is construed by Allison as a reason to cut fluid change intervals in half.

    Now that we have you able to slow the coach down and watch the gauges at the same time, here are two things you can do. First, turn on the retarder, put the lever in the second "on" position and note that it is unlikely that allowing the retarder to function will raise the temperatures beyond 210 to 230.

    Then leave the retarder switch on, but move the lever to the off position. Then do an agressive stop using the coach brakes from about 65 MPH. You will note the temperature will rise very fast, and will exceed the 230 degree marking on the gauge. From that it can be seen that if the retarder is engaged where it is needed the most, such as when descending long steep mountain roads fluid temperatures will easily exceed anything you have ever seen. You may be able to peg the transmission temperature gauge.

    The retarder system will function proportionately to the amount of braking force so with routine use of the retarder, even with the lever in the "0" position, but the switch on, tranmission fluids will be exposed to high temperatures.

    I have found that anticipating a steep descent, slowing to a reasonable speed at the crest of the hill, and descending in a lower gear allows the retarder to function, keeps the temperatures to a reasonable level, and does not require the use of brakes. If the hills are excessivly steep, the use of brakes may be required, at which point you, the driver, need to determione if you wish to supplement the retarder with braking (and the higher fluid temperatures), or to temporarily turn off the retarder and apply heavy braking to slow down below the target speed, and then re-apply the retarder. Either way you are going to spend money. You will shorten the life of the transmission fluid or you will wear out and heat up your brakes.

  9. #19
    Just Plain Jeff Guest

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    Gotchya, but I do something a bit differently.

    Let's take the Fancy Gap hill on I-77 just as an example. It is several miles of a descent, with I think about a 7% grade with some nifty twists and turns. What I do when approaching the grade is slow down. I mean, really slow down. If the other good folks along the roadway don't like it, they have 2 other lanes to do what they have to do.

    I downshift to the point where the camper feels as controllable as possible. This is not freewheeling; but a controlled descent. If my target speed, for example, is say 40, and I am sorry I am watching the road here, not the gauges, and feel that the coach is picking up too much speed for the remainder of the trek toward gravity, I do use the brakes and bring the speed again way down to what feels like a mangeable point. Usually that is only required once.

    Figure it this way; assume you are a blue-hair lady in a Focus who isn't sure which parking spot is closest to the IGA. Since you don't/shouldn't want to walk away from it all, maintain complete control.

    Somewhere someone posted that if you go down the hill at the same speed you went up the hill, it would be about right. I go slower than that.

  10. #20
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    Talking Exactly What I have been Saying

    Quote Originally Posted by Jon Wehrenberg View Post
    Either way you are going to spend money. You will shorten the life of the transmission fluid or you will wear out and heat up your brakes.
    That guys is exactly what I have been saying Spend money on brakes and all that come with them, or spend money on twice the number of trans. fluid changes. I'll bet the brakes overhaul cost is more than transmission fluid and filter replacements ?

    Thanks Jon, for clearing that up, even though the Thread Police should revoke your typing license, you too Jeff ?

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