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Black Tank Dump Valve

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   So, my black tank slide valve has a few years on it, never leaks and slides in n out fairly smooth n easy, HOWEVER, if the black tank is totally full it's hard to pull at first (maybe until pressure is reduced ?) until it gets to maybe 1/4 or so open and the rest is easy. Ima thinking and hoping ? that's due to the higher pressure against it ONLY when the tank is full and there's no other serious problem ? What say you fine gentlemen ? Its  not hard or expensive to change it out but no sense in doing so if this is typical. I haven't noticed any change in this like forever..

 John T   Enjoys routine and preventive maintenance when back home in the shop, much better than if on the road for sure !!


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Yep Kirk, I have been dolng that several years.. I drilled a hole where I shoot in lube regularly and it seems to help EXCEPT for that first bit when the tank is full........As long as she seals well and all the rest of the push/pull is okay I guess I will just have to live with it, but wondering if other gents had the same experience?? I always keep the black tank well flushed and cleaned out .. 

 Oh well there's always something it seems, goes with the territory

 Take care Kirk, thanks for the input

 John T

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Posted (edited)

Thanks gang ,,,,,,Indeed if I dump when the tank isn't so full that would reduce pressure.........However, it seems I get a more robust faster and maybe clear the tank better dump if its more on the full side, and that's usually when I do it (not to say I couldn't change if necessary) oh well such it is ...I'm a believer in plenty of water and good flushing and rinsing so I will just live with it and perhaps try a new valve see if it matters, even though mine seals well and slides smooth n easy otherwise (yes I keep it lubed as Kirk mentioned) .

I mostly was just wondering if other gents had the same experience (and its causes if known) or am I the only one ?

 Happy camping everyone, best wishes

John T


Edited by oldjohnt
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  • 3 weeks later...


After investigation I have come to a couple conclusions IN MY OPINION:

1) I believe its natural and to be expected when the tank is full that creates more pressure against the slide dump valve so it's just a tad bit harder to pull INITIALLY ...

2) For a few years I used the old trick of drilling a small home (plugged of course after lubrication) in the side top by the handle to spray in some lube and silicone spray seemed to lubricate and ease valve operation HOWEVER some time back I didn't have any silicone and used white lithium spray grease I THINK THAT CAUSED THE SLIDE ACTION TO BECOME HARD AND DIFFICULT TO PULL OPEN WHEN THE TANK WAS FULL ????? I say that because the seal area had an accumulation of the white thicker lithium grease. 

Moral of the story I WILL NO LONGER USE WHITE LITHIUM SPRAY GREASE (light silicone instead) to lube the slide dump valve. That may or may not have been the cause ?? but a new valve has cured the problem for now at least.

 Yall have a good day now best wishes

 John T  Happy Camper back home again in Indiana for a while. This summer I re installed my four rooftop solar panels about 1.5 inches above the roof surface (allows more air circulation under panels) as they were closer before which I think made them operate at a higher temp and less efficient ??? Time will tell but thats my belief



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I think you're right John! Sometimes heavy grease can create more problems than it alleviates. Once in a great while I'll pour some valve lubricant into my tanks just before an unused period, and it seems to help the slider valve move easier.

Welcome back to hot weather!

Edited by Ray,IN
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