Black Tank Slide Valve replacement

H

henry davis

New member
Dec 21, 1999
1,344
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Hi folks,

Today's challenge was to remove and replace the 3" slide valve on the black
tank.

Problem #1 - I pumped the tanks down using my macerator with the rear
setting low. Then raised the coach using the airbags and 6" ramps. When I
removed the macerator from the slide valve assembly I "caught" about 3
gallons of goop and water. About 1 gallon went into the catch bucket - the
rest went everywhere. Question - has anybody else had this problem with a
macerator installation? I would have thought that the level was well below
the opening.

Problem #2 - the new Thetford valve is leaking from the tank side seal.
Which direction does the o-ring seal go on the valve? (there is a taper tot
the o-ring).

Thanks for any help. I'm cleaned up now, the warehouse floor is
disinfected, and the mess is diluted...

Henry

Henry Davis Consulting, Inc / new product consulting
PO Box 1270 / product readiness reviews
Soquel, Ca 95073 / IP reviews
ph: (831) 462-5199 / full service marketing
fax: (831) 462-5198
http://www.henry-davis.com
 
I have a broken valve also, mine is cracked. I have been wondering if I
should try and fix it, or replace the whole tank...... after hearing this,
think I will replace the whole tank....I still have the original drain pipe
in connection with the Macerator, guess I will dump that also before I
remove the tank.... Not on of those great jobs we have to do on these rigs.

Are you going to drop the tank or fix it in place ?
gene

>Hi folks,
>
>Today's challenge was to remove and replace the 3" slide valve on the black
>tank.
>
>Problem #1 - I pumped the tanks down using my macerator with the rear
>setting low. Then raised the coach using the airbags and 6" ramps. When I
>removed the macerator from the slide valve assembly I "caught" about 3
>gallons of goop and water. About 1 gallon went into the catch bucket - the
>rest went everywhere. Question - has anybody else had this problem with a
>macerator installation? I would have thought that the level was well below
>the opening.
>
>Problem #2 - the new Thetford valve is leaking from the tank side seal.
>Which direction does the o-ring seal go on the valve? (there is a taper tot
>the o-ring).
>
>Thanks for any help. I'm cleaned up now, the warehouse floor is
>disinfected, and the mess is diluted...
>
>Henry
>
>
>Henry Davis Consulting, Inc / new product consulting
>PO Box 1270 / product readiness reviews
>Soquel, Ca 95073 / IP reviews
>ph: (831) 462-5199 / full service marketing
>fax: (831) 462-5198
>http://www.henry-davis.com
>
>
Genef -- 77PB/ore/ca
GMC MOTORHOME INFORMATION
mr.erf
http://www.california.com/~eagle/
 
>
>Problem #2 - the new Thetford valve is leaking from the tank side
>seal. Which direction does the o-ring seal go on the valve? (there
>is a taper tot the o-ring).
>
Henry - the Thetford o-ring should have some small indentations in
one side that fit around the small screw heads that hold the
stainless steel plate to the plastic part of the valve. If these are
not lined up properly it could hold the gasket away from the sealing
surface and cause a leak. I believe that this puts the tapered part
toward the tank fitting.

Emery
 
>Are you going to drop the tank or fix it in place ?
>gene



I'd like to fix it in place if I can. I know that there's more stuff in the
tank and don't want to have to mess with it now. But I may end up with no
option. IF I drop the tank, I'll buy a new one.

Henry
 
>>Problem #2 - the new Thetford valve is leaking from the tank side seal.
>>Which direction does the o-ring seal go on the valve? (there is a taper
>>tot the o-ring).
>Henry - the Thetford o-ring should have some small indentations in one
>side that fit around the small screw heads that hold the stainless steel
>plate to the plastic part of the valve. If these are not lined up
>properly it could hold the gasket away from the sealing surface and cause
>a leak. I believe that this puts the tapered part toward the tank fitting.


You're right. I did put the o-ring on with the taper towards the tank. I'll
check to see if it slipped while installing.

Henry
 
Just curious, but is the valve at the tank necessary with a mascerator? I'm
planning on a second valve after the mascerator for an "emergency" dump
provision and wonder if it's necessary that the first valve seal tightly(of
course, mine leaks)?

Patrick

>

>
> >Are you going to drop the tank or fix it in place ?
> >gene
>
> I'd like to fix it in place if I can. I know that there's
> more stuff in the tank and don't want to have to mess
> with it now. But I may end up with no option. IF I drop
> the tank, I'll buy a new one.
>
> Henry
>
 
>Just curious, but is the valve at the tank necessary with a mascerator? I'm
>planning on a second valve after the mascerator for an "emergency" dump
>provision and wonder if it's necessary that the first valve seal tightly(of
>course, mine leaks)?

On my coach the macerator is not capable of maintaining a water tight seal.
So, there's an annoying drip at the outlet. The rate of dripping depends on
the fullness of the tank.

JABSCO shows a full cutoff valve between the black tank and the macerator
pump in all of the installation pictures. SO, I'd say that you need the
slide valve to function properly. Maybe someone else has plumbed a
macerator without the slide valve.

Henry
 
Thanks Henry - I guess I already knew that would be the answer, but one can
hope. At least my tank is empty right now...

Patrick

>

> >Just curious, but is the valve at the tank necessary with a
> mascerator?
>
> On my coach the macerator is not capable of maintaining a
> water tight seal. So, there's an annoying drip at the outlet.
> The rate of dripping depends on the fullness of the tank.
>
> JABSCO shows a full cutoff valve between the black tank and
> the macerator pump in all of the installation pictures. SO,
> I'd say that you need the slide valve to function properly.
> Maybe someone else has plumbed a macerator without the slide
> valve.
>
> Henry
>
>
 
IMO , yes I think you need the tank valve. You would not want the solids
to pack into the macerator . With the tank valve shut most of the solids
slosh around in the tank and become liquid. I usually shut off the tank
valve and let the pump run for a while, I hope this gets most of the
residual out of the pump , lets me think the pump and lines as clear
anyway....

gene

>Just curious, but is the valve at the tank necessary with a mascerator? I'm
>planning on a second valve after the mascerator for an "emergency" dump
>provision and wonder if it's necessary that the first valve seal tightly(of
>course, mine leaks)?
>
>Patrick
>

>>

>>
>> >Are you going to drop the tank or fix it in place ?
>> >gene
>>
>> I'd like to fix it in place if I can. I know that there's
>> more stuff in the tank and don't want to have to mess
>> with it now. But I may end up with no option. IF I drop
>> the tank, I'll buy a new one.
>>
>> Henry
>>
>
Genef -- 77PB/ore/ca
GMC MOTORHOME INFORMATION
mr.erf
http://www.california.com/~eagle/
 
Henry,
When I rebuild my valve last fall I was able to get the tank clean and
empty, took a while but no mess. When I reinstalled the Thetford valve
back on the tank I also used a silicone sealer along with the O-ring to
insure the seal to the tank flange. Worked nice no leaks and the valve
works great.
- --
J.R. Wright
GMC GreatLakers
77 Eleganza II
Michigan

>
> Hi folks,
>
> Today's challenge was to remove and replace the 3" slide valve on the black
> tank.
>
> Problem #1 - I pumped the tanks down using my macerator with the rear
> setting low. Then raised the coach using the airbags and 6" ramps. When I
> removed the macerator from the slide valve assembly I "caught" about 3
> gallons of goop and water. About 1 gallon went into the catch bucket - the
> rest went everywhere. Question - has anybody else had this problem with a
> macerator installation? I would have thought that the level was well below
> the opening.
>
> Problem #2 - the new Thetford valve is leaking from the tank side seal.
> Which direction does the o-ring seal go on the valve? (there is a taper tot
> the o-ring).
>
> Thanks for any help. I'm cleaned up now, the warehouse floor is
> disinfected, and the mess is diluted...
>
> Henry
>
> Henry Davis Consulting, Inc / new product consulting
> PO Box 1270 / product readiness reviews
> Soquel, Ca 95073 / IP reviews
> ph: (831) 462-5199 / full service marketing
> fax: (831) 462-5198
> http://www.henry-davis.com
 
1. I don't have a macerator pump so I didn't have that problem.
I flush the tank with a bleach solution to clean the tank first.
2. The valve should have a pvc lip for pipe connection, this side face out.
Use lots of silicon cork. the screw fitting for the mounting screw on my
broke off, I have to drill thru and use nut and bolt. HTH.

Sam
> ----------
> From: gene[SMTP:mr.erf]
> Reply To: gmcmotorhome
> Sent: Wednesday, June 28, 2000 8:11 AM
> To: gmcmotorhome
> Subject: Re: GMC: Black Tank Slide Valve replacement
>
>
>
> I have a broken valve also, mine is cracked. I have been wondering if I
> should try and fix it, or replace the whole tank...... after hearing this,
> think I will replace the whole tank....I still have the original drain
> pipe
> in connection with the Macerator, guess I will dump that also before I
> remove the tank.... Not on of those great jobs we have to do on these
> rigs.
>
> Are you going to drop the tank or fix it in place ?
> gene
>

> >Hi folks,
> >
> >Today's challenge was to remove and replace the 3" slide valve on the
> black
> >tank.
> >
> >Problem #1 - I pumped the tanks down using my macerator with the rear
> >setting low. Then raised the coach using the airbags and 6" ramps. When I
>
> >removed the macerator from the slide valve assembly I "caught" about 3
> >gallons of goop and water. About 1 gallon went into the catch bucket -
> the
> >rest went everywhere. Question - has anybody else had this problem with a
>
> >macerator installation? I would have thought that the level was well
> below
> >the opening.
> >
> >Problem #2 - the new Thetford valve is leaking from the tank side seal.
> >Which direction does the o-ring seal go on the valve? (there is a taper
> tot
> >the o-ring).
> >
> >Thanks for any help. I'm cleaned up now, the warehouse floor is
> >disinfected, and the mess is diluted...
> >
> >Henry
> >
> >
> >Henry Davis Consulting, Inc / new product consulting
> >PO Box 1270 / product readiness reviews
> >Soquel, Ca 95073 / IP reviews
> >ph: (831) 462-5199 / full service marketing
> >fax: (831) 462-5198
> >http://www.henry-davis.com
> >
> >
> Genef -- 77PB/ore/ca
> GMC MOTORHOME INFORMATION
> mr.erf
> http://www.california.com/~eagle/
>
 
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