# Need some advice - back flow install



## MarkToo (Dec 17, 2011)

I've got a six unit commercial plaza that needs to have the back flow survey, installs and testing done this week. 

I took a peek at the job today when I stopped by to get the owner's contact info etc. The water service and meter are located in a small mechanical room with exclusive access from the outside - none from inside the building. There are no drains in the small 4'x6' space and there is an electrical transformer mounted to the floor (phase converter maybe), and the walls are covered with E meters, disconnects, phone, alarm and whatnot.

Anyhow I need to install an RPZ in this area and have been contemplating how to rig a catch drain for the device. The exterior walls are 8" block and there is enough space beside the man door to poke through with whatever I decide to do. I need to consider frost protection and icing on the outlet.

Initially I was thinking an 11/2 trap with a barbed fitting after the trap and some 3/8" condensate type poly through to the outside but then thought maybe 11/2 ABS (we don't use PVC) out and through to help against freezing.

Not really sure what the best plan of attack is here as it's a little odd. The RP's spit a bit sometimes and I don't want the floor mounted sparky stuff to get annoyed.

What do you think?


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## user7551 (Oct 21, 2011)

What size of RPZ are you putting in because a 3/8 poly line doesn't sound like it would be a large enough drain. Here in Texas whatever size the rpz is that's the size of the drain we have to put in.


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## HSP (Jan 14, 2012)

Most manufactures, manufacture RP Drain assembly’s that attach directly to the backflow device you’re installing, providing for proper drain sizing, air gap, etc. Drain doesn’t need to be trapped and since there shouldn’t be water in it you don’t really need to worry about freezing.


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## MarkToo (Dec 17, 2011)

_"What size of RPZ are you putting in because a 3/8 poly line doesn't sound like it would be a large enough drain. Here in Texas whatever size the rpz is that's the size of the drain we have to put in."
_
That's probably a good rule of thumb. The RPZ is 1".

_"Most manufactures, manufacture RP Drain assembly’s that attach directly to the backflow device you’re installing, providing for proper drain sizing, air gap, etc. Drain doesn’t need to be trapped and since there shouldn’t be water in it you don’t really need to worry about freezing."
_
The trap is only to keep critters from crawling inside. No there shouldn't be water in it but, we all know this can happen and that's the reason for setting something up to direct it outside. The freezing I'm concerned with is on the exit of the building not the trap itself.

We've got sump pump discharges that exit to the outside plumbed with 11/2" so I guess this is no different.

Unless someone's got some insight, this is what I'll do.


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## Tommy plumber (Feb 19, 2010)

Make sure you plan well for the drainage provision. That could come back to bite you. Are there any floor drains in the mechanical room where the RPZ will be located? If not, I would recommend to customer that floor drain(s) should be installed in addition to a dedicated drain line for the backflow.


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## user7551 (Oct 21, 2011)

MarkToo said:


> _"What size of RPZ are you putting in because a 3/8 poly line doesn't sound like it would be a large enough drain. Here in Texas whatever size the rpz is that's the size of the drain we have to put in."
> _
> That's probably a good rule of thumb. The RPZ is 1".
> 
> ...



If you put a trap on the rpz drain it will not stand a chance to carry all the water out if the relief valve ever opens all the way


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## Plumber patt (Jan 26, 2011)

Agreed, don't trap the drain. The rp must drain indirectly, so the installation of a trap is redundant because your critters can still enter above the trap. I agree that a floor drain should be installed, if you straight pipe it outside, in the winter a cold draft may shoot right up the drain and could possibly freeze the device.


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## BFlow (Apr 14, 2011)

If the relief valve opens fully, it's doubtful the drain, trapped or not, will handle the discharge. Mechanical rooms with no drains are just dumb.
Pipe the meter and rpz to another rooom with a drain, or get your inspector to approve a dcva, isolate the hazard downstream with an rpz.

Sticking the pipe out the wall is a hack job, you might as well install the rpz upside down. 

A 2" rpz has a discharge rate of around 178 gpm, convert that to FU, drain size 8-10"


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## user7551 (Oct 21, 2011)

BFlow said:


> If the relief valve opens fully, it's doubtful the drain, trapped or not, will handle the discharge. Mechanical rooms with no drains are just dumb.
> Pipe the meter and rpz to another rooom with a drain, or get your inspector to approve a dcva, isolate the hazard downstream with an rpz.
> 
> Sticking the pipe out the wall is a hack job, you might as well install the rpz upside down.
> ...



before you run your mouth at least read the whole thread, the rpz in question is a 1 in rpz . The maximum discharge rate is 40 gpm and that is if the building has 100 psi so lets say the building pressure is 50 psi that makes the discharge rate 30 gpm . As for your 2 inch rpz having 178 gpm thats only if the pressure is 160 pounds get real guy . Whos the hack? also recalculate your drain sizing for a 178gpm because again your wrong . Are you sure your not a hack?


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## Mississippiplum (Sep 30, 2011)

BFlow said:


> If the relief valve opens fully, it's doubtful the drain, trapped or not, will handle the discharge. Mechanical rooms with no drains are just dumb.
> Pipe the meter and rpz to another rooom with a drain, or get your inspector to approve a dcva, isolate the hazard downstream with an rpz.
> 
> Sticking the pipe out the wall is a hack job, you might as well install the rpz upside down.
> ...


You must be following that united plumbing code :laughing:

sent from the jobsite porta-potty


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## Plumber patt (Jan 26, 2011)

I've talked to watts reps before, they have told me on numerous occasions that the likelihood of an rp dumping at that rate is slim to none. For the most part it's just nuisance dumping and what ever the size of the discharge on the air gap fitting will suffice.


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## user7551 (Oct 21, 2011)

Plumber patt said:


> I've talked to watts reps before, they have told me on numerous occasions that the likelihood of an rp dumping at that rate is slim to none. For the most part it's just nuisance dumping and what ever the size of the discharge on the air gap fitting will suffice.



your absolutely right ,but on the offhand chance a floor drain would be nice in the room . Something else to think about is would you rather it dump in a room that might not have to many visitors or would rather it dump outside where it can be seen dumping and get the attention it needs alot quicker.


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## Plumber patt (Jan 26, 2011)

If there was no transformer sitting on the floor, I'd just pipe towards the floor and leave it that way, but with the electrical hazard, I'd say outside is the best solution for that scenario short of piping in a proper floor drain


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## user7551 (Oct 21, 2011)

Plumber patt said:


> If there was no transformer sitting on the floor, I'd just pipe towards the floor and leave it that way, but with the electrical hazard, I'd say outside is the best solution for that scenario short of piping in a proper floor drain



they make a rpz drain adapter without an airgap but you would have to talk to your inspector about using its not for the situation your in but could be used for it , In your situation he might allow it because of all the electrical in the room.


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## BFlow (Apr 14, 2011)

playme1979 said:


> before you run your mouth at least read the whole thread, the rpz in question is a 1 in rpz . The maximum discharge rate is 40 gpm and that is if the building has 100 psi so lets say the building pressure is 50 psi that makes the discharge rate 30 gpm . As for your 2 inch rpz having 178 gpm thats only if the pressure is 160 pounds get real guy . Whos the hack? also recalculate your drain sizing for a 178gpm because again your wrong . Are you sure your not a hack?


I havnt even begun to run my mouth. 
I hope home depot gets those sharkbites back in stock soon so you can get working again.

I'm not your unlicensed Mexican helper, you can't talk to people that way. You got offended because you drain on the floor, yes your a hack.

I'll be back around lunch to call you more names.


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## ILPlumber (Jun 17, 2008)

Just to be clear. We won't be disrespecting each other or name calling.

Thanks for your mandatory cooperation.

ILP


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## user7551 (Oct 21, 2011)

BFlow said:


> I havnt even begun to run my mouth.
> I hope home depot gets those sharkbites back in stock soon so you can get working again.
> 
> I'm not your unlicensed Mexican helper, you can't talk to people that way. You got offended because you drain on the floor, yes your a hack.
> ...


Like I said , all the numbers you posted are not just wrong they are ridiculously wrong . Show me one spot where I said to run it on the floor? I'm waiting . If you have a plumbing license of any kind that would just be so wrong in so many ways . Go back to the code book you use and check your numbers you posted.


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## user7551 (Oct 21, 2011)

[/QUOTE]I'm not your unlicensed Mexican helper[/QUOTE]

My Mexican helper is licensed.


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## user7551 (Oct 21, 2011)

:thumbup::jester:A little learning is a dangerous thing, but a lot of *ignorance* is just as bad


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## Plumber patt (Jan 26, 2011)

Love the new guy running his mouth.... No respect these days lol


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## MarkToo (Dec 17, 2011)

OK, anyhow...

I piped it up today. Ended up just running 11/2 out through the block wall with a turn down at the outlet.

It's a bit of an odd situation and the two other local plumbers I talked to both kinda shook their heads a bit but, we all agreed that written notification to the building owner regarding the possible issues with a full port dump would be prudent. 

It's installed, tested, survey complete, functional (with caveats), and looks good to boot.


As a side note:

I sent my 2nd year (2 weeks on the job with me now), apprentice off first thing to get started on jigging the pipe hangers etc., while I finished up something from the previous day. We've done a couple BF devices in the last couple weeks and he's been keen to learn what I've been drilling him.

He messages me about a half hour into his job - prior to hanging the device and says, "Aren't we supposed to be putting an RPZ in here"? I tell him ya, that's what were putting in and that's what the wholesaler packaged up for this job. He tells me well, "An RPZ is supposed to have a drain on the bottom, and this doesn't have a drain".

I like this kid - he's on the ball. Even though he's not really sure what's going on, he's thinking. He was right. They sent a DCVA. Most apprentices I've had in the past would have just gone ahead and started putting things together. He did what he could 'till the right part showed up and on he went. He saved us a couple hours of nonsense today.

A happy boss.


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## Plumber patt (Jan 26, 2011)

Rare find, teach him well, we need more good plumbers out in the field. Far too many morons in our trade


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## user7551 (Oct 21, 2011)

Hes certainly a keeper , he ask questions. That's a good thing


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## gladerunner (Jan 24, 2009)

My apprentice would have gotten the drill out and added the hole


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## MarkToo (Dec 17, 2011)

gladerunner said:


> My apprentice would have gotten the drill out and added the hole



LMAO - He used to work for me.:laughing:


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## Plantificus (Sep 17, 2009)

Plumber patt said:


> Agreed, don't trap the drain. The rp must drain indirectly, so the installation of a trap is redundant because your critters can still enter above the trap. I agree that a floor drain should be installed, if you straight pipe it outside, in the winter a cold draft may shoot right up the drain and could possibly freeze the device.


I had one freeze just last week... the ice buckled the cover plates and made the rebuild impossible (whole plaza was out of water and we couldn't get the cover plates from our supplier for 4 days) he decided to go with a new 2 in 909 RPZ... that'll hurt the wallet


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## Piper34 (Oct 10, 2011)

In Suffolk cty. On L.I. Our water supplier demands RPZ drains be piped outside with screen cover to prevent vermin .Living in a freeze zone I usually install a gem cap cut 7/8 of the way around to act as a flapper keeping cold wind out .Drains are always sized for the unlikely event of catastrophic failure in which whatever size valve you install could have maximum flow rate .I believe for 2" A 12x12 pan with 6"drain is required .For 1"A12x12pan with 4"drain is typical .They sound big but they are very strict if you want a meter in a new service you comply.


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## Plumber71 (Dec 20, 2010)

By code you are not allowed to dump an water onto outside the property . And being commercial it is even worst , by the water dept. standard it is ok . But if you had it inspect by the town , the plumbing inspector would fail you . That what is good about L.I , they don't want approved plains draw up , in the five boro's , you couldn't do that .


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