# Commercial kitchen DWV repair



## smellslike$tome (Jun 16, 2008)

Ok, I think I'm going to get hammered on this one because I feel like this is something I should know but don't.

I have a 4" pvc drain that receives waste from a large church kitchen. I forget the original reason for the repair. I use the term loosely because the repair has failed twice. Originally we cut out about a foot of pipe (there may have been some fitting there to begin with) and because we don't own a pipe stretcher or compressor, we put in a new piece of pipe with double banded shielded couplings. The problem is that this line is receiving very hot water from a dishwasher and over time the cut ends of the pipe soften and taper in. When this tapering happens the mechanical couplings lose their grip and the expansion and contraction of the pipe leave us with either a leaking coupling or an out and out separated pipe.

So I've given up on any kind of mechanical coupling which leaves me with only three options as far as I can see.

1. I can put in a ridiculous offset in the line so I can get some glued fittings to go together. I don't like this idea.

2. I can repipe approximately 20 feet of pipe until I reach an existing offset. This sounds simple but it's not because I will have to bust out around the pipe through two block walls and reseal after I'm done. I'm leaning this way.

3. I can use a telescopic repair coupling. Even though I'm not sure these are even code approved, (because they make their seal by means of an o-ring) I was standing at the supply house counter about to purchase one when I saw in raised lettering on the coupling itself "For cold water use only". So I nixed that idea not wanting to throw away $50 on something that had a very high probability of failure.

My question is, do I have any other options? Is there a simple solution that I should know about but don't.


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## rombo (Jul 17, 2008)

I have done this exact repair. Take a 4" coupling get a hole saw just big enough to remove the stop of the coupling, file if necessary. You now have a slip coupling. Way better than a telescopic if you ask me.


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## plumbpro (Mar 10, 2010)

smellslike$tome said:


> Ok, I think I'm going to get hammered on this one because I feel like this is something I should know but don't.
> 
> I have a 4" pvc drain that receives waste from a large church kitchen. I forget the original reason for the repair. I use the term loosely because the repair has failed twice. Originally we cut out about a foot of pipe (there may have been some fitting there to begin with) and because we don't own a pipe stretcher or compressor, we put in a new piece of pipe with double banded shielded couplings. The problem is that this line is receiving very hot water from a dishwasher and over time the cut ends of the pipe soften and taper in. When this tapering happens the mechanical couplings lose their grip and the expansion and contraction of the pipe leave us with either a leaking coupling or an out and out separated pipe.
> 
> ...


I don't know what they are called, but there is a repair coupling that glues into pipe on one side and you can glue a coupling onto the other side and go on from there. The disadvantage is a slight "bottle neck" in the pipe. 
Don't know if it would work but maybe worth a try.


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## user4 (Jun 12, 2008)

Charlotte makes a stopless coupling, around here we call them repair couplings, make sure you mark the pipe so you get it even on both sides.


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## Tommy plumber (Feb 19, 2010)

Killertoiletspider said:


> Charlotte makes a stopless coupling, around here we call them repair couplings, make sure you mark the pipe so you get it even on both sides.


 



If you do this, use ALOT of pvc cement, the slip couplings (as I call them) are a looser fit than a regular coupling. It'll leak if you don't slop on the cement.


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## rombo (Jul 17, 2008)

I have only ever got slip couplings in sdr. Didn't know they were even made in abs/pvc


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## Protech (Sep 22, 2008)

Any chance of running around the block with 4 90's? If you have that much heat going through pvc a little expansion "U" wouldn't be a bad idea anyway.

Throw a cleanout on each side as jetting through that "U" is going to be a pain years later.




I don't trust those slip couplings. I would only use one as an absolute last resort. They are right there with Schwinn couplings IMHO. :laughing:


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## greenscoutII (Aug 27, 2008)

Killertoiletspider said:


> Charlotte makes a stopless coupling, around here we call them repair couplings, make sure you mark the pipe so you get it even on both sides.


Toiletspider beat me to the punch. I've used these dozens of times. See if you can buy some slower setting glue to use with these. You have to work FAST even so!


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## ckoch407 (Sep 30, 2009)

As said the slip couplings are last resort. If it outweighed going through the block, I would consider a piece of CI instead of the PVC as the replacement section, and possibly a style 38 Dresser coupling if I didn't trust the shielded couplings any more.


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## user4 (Jun 12, 2008)

greenscoutII said:


> Toiletspider beat me to the punch. I've used these dozens of times. See if you can buy some slower setting glue to use with these. You have to work FAST even so!


We always used heavy body slow set cement designed for gluing sch 80 pipe, it was gray in color and worked quite well.


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## greenscoutII (Aug 27, 2008)

Killertoiletspider said:


> We always used heavy body slow set cement designed for gluing sch 80 pipe, it was gray in color and worked quite well.


Yeah, my old boss swore by that stuff. I have to admit using that heavy body glue makes it just about impossible to have a leak. Too bad it doesn't seem to be available in quart size cans....


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## plbgbiz (Aug 27, 2010)

In the absence of a slip coupling, I have used a rotozip to create one. Also the large dresser style compression couplings might be a second option. I like the idea of it being glued solid but the compression coupling gives repair access down the road.


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## 504Plumber (Jan 26, 2011)

I would also like to throw my .02 in. If you use a slip couplig make sure everything is dry dry dry! For some reason I've never had luck with them on a vertical wc line if the flapper is bad or if there is excess moisture in the line. On a horizontal you should be ok, just make sure inside and out is dry and do everything quick.


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## vinpadalino (Aug 27, 2010)

What about 2 unions?


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## GREENPLUM (Jul 27, 2008)

How hot is the discharge?

Repair/Slip Coupling


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## RealLivePlumber (Jun 22, 2008)

Howza bout some cast iron, with a double hubbed fitting?

Or get some  dare I say it, 4" copper tube.

Lets not forget we are not limited to plastic-fantastic.


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## Pipe Rat (Apr 5, 2009)

Never had a problem with the solvent weld repair couplings. Are you using solid PVC or foam core?


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## rombo (Jul 17, 2008)

What temps are we talking. I have gone in to restaurants where the dishwasher was piped in pvc and the temperature was set way too high on the unit. Had to turn down temp and repipe entire run.

In a cases where extreme temps are required copper is a must. Our code states that any discharge in excess of 167f must be cooled before entering a drainage system.


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## vinpadalino (Aug 27, 2010)

rombo said:


> What temps are we talking. I have gone in to restaurants where the dishwasher was piped in pvc and the temperature was set way too high on the unit. Had to turn down temp and repipe entire run.
> 
> In a cases where extreme temps are required copper is a must. Our code states that any discharge in excess of 167f must be cooled before entering a drainage system.


Maybe I'm missing something but I had to run high pressure steam pipe in PVC.


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## Protech (Sep 22, 2008)

:wacko:

:no:



vinpadalino said:


> Maybe I'm missing something but I had to run high pressure steam pipe in PVC.


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## plbgbiz (Aug 27, 2010)

vinpadalino said:


> Maybe I'm missing something but I had to run high pressure steam pipe in PVC.


PVC can start to breakdown shortly after 140deg. I don't see steam happening in PVC.


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## rombo (Jul 17, 2008)

I am talking about dwv system 15 made by ipex. Not sure if there are types of pvc that can withstand steam but i doubt it
.


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## PlumberShep (Sep 22, 2010)

If the discharge from the dishwasher is 140f or above I would redo that waste in copper.I'm not sure that I fully understand your description though.Are you talking about 2" pvc from the dishwasher penetrating a block wall and discharging indirectly into a floor sink?


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## SPH (Nov 4, 2008)

I'd redo that whole drain line with pipe rated for the temperature it's receiving. You don't want to have to make the repair then get called back because of another failed joint along the line. Customer will wonder why you never warned them to start with.


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## Eric (Jan 10, 2011)

I am not a big fan of 4" slip couplings as well. Pretty tough to work with.

I would get 4- PVC to No Hub transition fittings and clamp them using 4 band no hub clamps. 

The clamps will now be on the fittings instead of smooth pipe.


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## ranman (Jan 24, 2010)

no waste above 140 deg shall discharge into the plumbing system. (both codes) 

it should hit a receptor of some type to promote cooling. that has always been the hard part.


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## RealLivePlumber (Jun 22, 2008)

Commercial dishwasher shall drain indirectly, through an air gap.


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## Protech (Sep 22, 2008)

Install aqua-stat on discharge pipe wired to a motorizes dump valve. Valve dumps cold water in the line when hot waste is flowing. Done.


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## RealLivePlumber (Jun 22, 2008)

Protech said:


> Install aqua-stat on discharge pipe wired to a motorizes dump valve. Valve dumps cold water in the line when hot waste is flowing. Done.


Awful lot of work, moving parts, wiring, electricity. 

Then the aquastat gets knocked off, falls in the receptor, electrocutes someone. Solenoid valve goes bad, another call back. 

Inderect waste. Copper tube. Done.


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## smellslike$tome (Jun 16, 2008)

Ok, let me say thank you for everyone's response. I appreciate the input. 

I've got a little time (but not much) before the thing gives way again.

I'm leaning towards repiping to a place where I can get enough lateral movement of the (cut) pipes within an already occurring offset to get a fitting together. Hope that makes sense. 

I have this little smart a$$ saying that I throw out to customers sometimes (always after I have successfully solved a difficult problem), "the pipe obeys the plumber, the plumber does not obey the pipe". They never really fully appreciate what the big whoop is all about but I just like saying it. In this case, the pipe will indeed obey the plumber but the plumber will be forced to exploit the weaknesses of the pipe. Wrestling with 4" schedule 40 is not a lot of fun atop a ladder and if you don't get it right the first time it turns into a hideous mess (I like my pipes to look pretty :laughing.

The slip coupling idea has a certain appeal, and if it were smaller diameter pipe I probably wouldn't hesitate to do it but this is 4", there is no chance of getting the line completely dry so I will be using blue glue and I had to use a good bit of force at this particular spot just get enough lateral movement in the piping to get the mech coupling on, I don't see me having a lot of success getting a slip coupling on.

No dresser coupling. The only time I use them is when they are buried in the ground, otherwise I just don't want to see them.

I thought about the unions, but again, no pipe stretcher. 

Not sure what that other "coupling" was that produced a "slight narrowing of the pipe" but that is a definite code violation.

PT, methinks thou art an commodian with your "dump valve", :yes:.

As for transitioning to some other type of piping, c'mon, really!? It's about 60' to the grease pit and frankly I don't have a big enough pair to tell these people that the best solution to their problem is to cut out all that sched 40 pvc and replace with 4" dwv copper.

I don't know the terminal temp because whoever installed the 120 gal wh didn't see fit to install any temp reading device of any kind, besides the dw has a heat booster anyway. In any event I'm sure it's greater than 140*.

Anyway , thanks again for all the input.


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## rombo (Jul 17, 2008)

On many dishwashers the boost can be adjusted. Might be something to look in to. 

As for not being able to use a slip coup due to water in line. I would install a 4" line C.O upstream of repair, and plug it with a inflatable test grenade if possible.


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## Protech (Sep 22, 2008)

I don't know what was so funny. Perhaps you could fill me in after you figure this out.



smellslike$tome said:


> Ok, let me say thank you for everyone's response. I appreciate the input.
> 
> I've got a little time (but not much) before the thing gives way again.
> 
> ...


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## Protech (Sep 22, 2008)

RealLivePlumber said:


> Awful lot of work, moving parts, wiring, electricity.
> 
> Then the aquastat gets knocked off, falls in the receptor, electrocutes someone. Solenoid valve goes bad, another call back.
> 
> Inderect waste. Copper tube. Done.


It's allot let expensive than installing new metal pipe now isn't it.

It is ideal? No. Will it fix the problem of running high temp water through PVC waste? Yes.


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## OldSchool (Jan 30, 2010)

Is this a straight run of pipe... if so why not do some type of offset for thermal expansion


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## Redwood (Sep 8, 2008)

Protech said:


> Install aqua-stat on discharge pipe wired to a motorizes dump valve. Valve dumps cold water in the line when hot waste is flowing. Done.


If I was going to do that I'd simplify it by eliminating the aquastat and pick up power for the cold water solenoid off the dishwasher drain solenoid. When it's draining the cold water is running....


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## breid1903 (Feb 8, 2009)

rlp. if you can't install the aqua-stat safely, well you could hire an electrician. i have my electrician do mine. lol. breid.............:rockon:


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## Protech (Sep 22, 2008)

Even better. K.I.S.S.



Redwood said:


> If I was going to do that I'd simplify it by eliminating the aquastat and pick up power for the cold water solenoid off the dishwasher drain solenoid. When it's draining the cold water is running....


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## Widdershins (Feb 5, 2011)

I'm having a hard time understanding how the DW is connected to the drainage system.

Surely it isn't a direct connection, right?

We use a stainless indirect receptor on all of our installations -- And if I were experiencing the problems being described in this thread -- I'd get a higher capacity indirect receptor and a Schedule 80 or 40 Canplas Flow Control and meter the amount of water entering the drainage system.


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