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I have come across several 3-compartment sink drains and commercial dishwasher drains with pvc pipe and it was glued with regular pvc cement and it will come apart at the glue joints I'm assuming from the ultra hot water flowing into the pvc pipe,I'm thinking about using multipurpose on these drained from now on,think this will be ok and what do you use in these hot water pvc drains??
 

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I have come across several 3-compartment sink drains and commercial dishwasher drains with pvc pipe and it was glued with regular pvc cement and it will come apart at the glue joints I'm assuming from the ultra hot water flowing into the pvc pipe,I'm thinking about using multipurpose on these drained from now on,think this will be ok and what do you use in these hot water pvc drains??
Are you using primer? I've never had an issue with pvc and heat. Maybe let it sit for a couple hours before running the super hot water? Ideally when it sets up the glue joint should be as strong as the rest of the pvc, that's why they call it solvent WELDING. I know not all joints are perfect. I see no reason why multipurpose glue wouldn't be worse since regular pvc glue is designed to be chemically identical to the pipe itself once it cures.

Usually with sanitizing dishwashers we run some no-hub for the first 10/20' or rarely copper. We also usually run the discharge into a floor drain as an air-gap. The floor drain will be 3" no-hub. These two steps usually dissipate enough of the heat.

I've used pvc straight off a dishwasher before though with no issues. I would think a 3 bay sink wouldn't have as hot water. I find it odd that you find so many joints failing. Are your joints failing or just those you find from others?
 

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I have not seen any problems with pvc joints under 3 compartment sinks. I just use primer and pvc cement like on any other pvc. Now for a commercial dishwasher it's different as if it has a booster it gets up to 180F. In that case it should have castiron drain going in to a castiron floordrain and after 10'-20' it's cooled down enough to use plastic.

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My jurisdiction does not allow the use of PVC for these applications. I would argue that you should never use PVC for the drain from a commercial dishwasher as the temperature is so hot. I wouldn’t have guessed you’d have a problem under a three compartment sink though. Make sure you are using PRIMER and not CLEANER. There is a difference.
 

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.......... I would argue that you should never use PVC for the drain from a commercial dishwasher as the temperature is so hot......
I agree. Certain jurisdictions allow for chemical sanitization which doesn't require the extremely high temperatures.

I've only once used pvc on a high temp washer and it was a temp repair. I've seen it as a permanent fixture on a handful of high temp washers though and even in those situations it didn't fail as he described, mostly just sagged a lot.
 

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Discussion Starter #6
Are you using primer? I've never had an issue with pvc and heat. Maybe let it sit for a couple hours before running the super hot water? Ideally when it sets up the glue joint should be as strong as the rest of the pvc, that's why they call it solvent WELDING. I know not all joints are perfect. I see no reason why multipurpose glue wouldn't be worse since regular pvc glue is designed to be chemically identical to the pipe itself once it cures.

Usually with sanitizing dishwashers we run some no-hub for the first 10/20' or rarely copper. We also usually run the discharge into a floor drain as an air-gap. The floor drain will be 3" no-hub. These two steps usually dissipate enough of the heat.

I've used pvc straight off a dishwasher before though with no issues. I would think a 3 bay sink wouldn't have as hot water. I find it odd that you find so many joints failing. Are your joints failing or just those you find from others?
Definitely others,but I think the hot water is softening the glue over time causing it to faili have come across this at several micky Dee’s in the past and another one saturday
 

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Discussion Starter #7
Also they have their water heater turned up to 140 degrees or more on 3-comp sink and if all three vats are full of this scalding hot water I can see the hot water causing a glue joint to fail over time,that's a lot of hot water running thru that pipe,also I only have 18-24" on drain before it goes into vent in wall so no cast iron or copper can be used,they had the 3-comp sink and the dishwasher all tied into the same 2" pvc pipe
 

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We always use copper on commercial dishwashers
Pvc will melt.
Every commercial kitchen i have plumbed has a booster heater under the dishwasher the output is 180 degreesF
 

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I’ve remodeled a few commercial kitchens, replaced many three and four compartment sink drains. Never an issue with pvc. Commercial dishwashers dump into a floor sink here with an air gap. No problems there either.
 

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We always use copper on commercial dishwashers
Pvc will melt.
Every commercial kitchen i have plumbed has a booster heater under the dishwasher the output is 180 degreesF
Yes it should be but this micky dees was plumbed 22yrs ago and they used pvc on the sink and dishwasher
 

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I’ve remodeled a few commercial kitchens, replaced many three and four compartment sink drains. Never an issue with pvc. Commercial dishwashers dump into a floor sink here with an air gap. No problems there either.
I would dump this dishwasher into a floor sink IF it had one,all I can do is direct pipe it into the 3-comp sink drain,that's all we can do with it
 

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Watts 9D doesn’t cut it.... Someone help me with this one. It’s been a few years. Damn it. No sleep tonight and I don’t have that code book!
I was agreeing that commercial must dishwasher as an indirect waste. We actually can use a 9D here in conjunction with a watts 288a vacuum breaker. Although some towns require us to use a 009 testable double check and an 800m testable vacuum breaker.
 

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I was summer help pre apprentice in '68 on the Wayne State Medical center (Detroit). Plastic pipe rep came out and showed my journeyman ( traveler 70 yr old who ran for governor of Arkansas in 40's). The demo was for a toilet battery vent only 2". I watched carefully. "prime pipe after removing burs, apply cement to fitting first, then pipe....push together...1/4 turn...hold 60 seconds together with firm pressure....after he left the governor never did the 1/4 turn and held for 10 seconds. The water test looked like a fountain with all joints leaking.
Fast forward to 1980....travel job....GM plant Dayton Ohio for Forman Industries..Morrain engine i think....."You guys ever work on plastic conductors? Sure my partner said...also from Motown Local 98..."Good we get alot of leaks maybe cause its 10 inch conductors?"" So Larry starts the first joint prep sanding etc...I of course read the can of cement...at this time new 4th generation cement came out no holding 60 seconds required....but we must have got a load of the same 1st generation cement I was privy to in '68. The can said "....and hold 60 seconds>>" so the common issue in the trades is failure to not read the installation instructions...not to mention expired glue sitting in some trailer years bought by bean counters...we had no leaks but drug up when they told us we had to drive a drott and put the pipe up tooo"" We have operating engineers in Detroit" Larry told them...."weell in Dayton we do the crane operating...said Mr forman.. The simple point is your question on which glue??? The answer is in the manufacturers instructions, and with the internet a simple phone call to the manufacturer or their trade organization for guidance. You could have mixed brands of fittings and pipe etc....Hope this steers u in the right direction.
 
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