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miamicuse 12-21-2011 09:34 PM

Scupper drain installation advice needed
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In a previous thread I mentioned that I have a yankee gutter issue. This thread is to replace the roof drain that receives the runoff from those gutter.

Before pictures showing the existing roof drain and what it looks like below the roof deck.

To be honest, I couldn't find any roofer locally who have experience, so I researched it myself and decided I want to use a scupper drain, and hired a roofer who seemed willing to take on the challenge, but have never done one.

I settled on the Zurn Z187 drain at the bottom of this page.

The installation instructions are here but it is not entirely clear.

Here is a picture of the drain.

Here is what the roofer did.

First, he demo the existing portion of the gutter. Cut out the existing metal gutter liner, and the membrane over it.

Here is the existing metal liner that was on top of the gutter, one single piece.

Next, he built a depressed box with 2x4 and plywood to set the scupper drain into. That work is solid, the drain sits nicely in it.

Next, he laid a piece of lead flashing into this box. We debated whether it may be better to use aluminum or galvanized, but he felt better with lead because it is easier to manipulate. The flashing covers around the lip of the drain inlet. Then he applied some mastic over the top of the lead flashing to seal the flashing to the drain. This is where I am a bit confused. I know from the instructions, the flashing goes OVER the perimeter of the scupper drain. I am not sure where this black mastic is involved.

Then he applied some roofing paper on top of the lead flashing, and the roofing paper again goes over the "lip" of the drain. Then he added more of the sticky black mastic, and then threw some granules on top of that.

Then he put the silver colored metal "rim" on top, and secured with the bolts.

This created two problems.

First, between the drain lip and the clamping collar, are now many layers. Above the drain lip is a layer of mastic, then the lead flashing, then more mastic, then roofing paper, then more mastic then granules, then the collar. Is this right? I am thinking, all it is needed is the flashing. The granules, will end up causing leak, I think...right?

Second, because it has so many layers, the clamp collar now sits 1/4" above the bottom of the finished surface. That means there will be 1/4" of water always sitting there. If he just put the flashing over the lip, and cut the roofing paper around the edge of the collar, it will end up being flushed vertically.

So both the roofer and myself are not experienced with this. I looked at the installation instructions on Zurn, and it didn't say.

Would really appreciate some feedback on this. Thanks in advance!

AGWhitehouse 12-22-2011 12:22 AM

Holy Schnikies!! That is the wrong application for that drain, but you managed to hack up your roof system and get it to function...A typical scupper usually looks like this:

You really wanted to go with a traditional drain assembly that looks kind of like this: Notice it has a side drain port to connect to your existing down spout. Here's one installed:

As for the 1/4" Lip, that's pretty common in flat roof applications. Just make sure there is no real ponding (pools larger than a foot or two in diameter) and you'll be fine. A 1/4" of water at the lip won't be there for long and will evaporate off.

miamicuse 12-22-2011 12:51 AM

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We started off with the round roof drain. However the clearance below was not enough for a bottom inlet drain with an elbow added. If you look at picture #2, there is not much room below the deck to have the drain assembly concealed above the soffit. Secondly, since the gutter was sloped, putting in a round drain as is would mean the drain will be tilted up.

Which started me thinking of building a depressed box and using a scupper.

miamicuse 12-22-2011 12:52 AM

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Any comment about the clamp collar and the drain lip? Is the various layers there OK or should we clean it up and tweak it?

AGWhitehouse 12-22-2011 07:26 AM


Originally Posted by miamicuse (Post 800104)
Any comment about the clamp collar and the drain lip? Is the various layers there OK or should we clean it up and tweak it?

What you did looks fine. I was only surprised because that's an a-typical installation and they do make side discharge standard drains that would've accomodated the low clearance. The last part of my post addresses your lip issue. I don't see an issue with it.

miamicuse 12-22-2011 08:54 AM

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I was debating between a round drain with a side outlet vs a scupper drain. The issue with the side inlet round drain is the gutter is sloped, and I didn't want to put in a round drain with 12" diameter so the drain center end up sitting an inch higher than the low point. The low point is right at the edge so there is no way to put the drain in the center of it. Furthermore, it will also mean the elbow below has to tilt up a little to follow the gutter cross slope. So plumbing that will be a challenge.

I then decided whether it is a round drain or scupper, I should build a box or a nitch for it offset from the gutter a bit.

I ended up with the scupper which I noticed used a lot for balcony edges.

I am still wondering between the flashing collar and the drain lip, is it ok to have mastic and granules there or should just be flashing? I am concerned about leakage after this bakes in the sun and expansion contraction of the plywood box causing movements.

AGWhitehouse 12-22-2011 09:08 AM


Originally Posted by miamicuse (Post 800279)
I am still wondering between the flashing collar and the drain lip, is it ok to have mastic and granules there or should just be flashing? I am concerned about leakage after this bakes in the sun and expansion contraction of the plywood box causing movements.

You should be fine. The metal pan flashing extends to within the drain throat as shown in the second to last pic. The clamping ring is then only a measure to keep that flashing in place. Provided you "gooped" the bolt locations before and after you installed the clamping ring you should see no issues.

1985gt 12-22-2011 11:45 AM

It should be ok. The drain lead should have been large enough to land on the top of the box that was created. The existing roofing should have been overlapped by the drain lead. Also I hope he put mastic on both sides of the drain lead. Then he should have installed 2-3 plys of felt all set in mastic and over laped on to the existing roofing. Then a granulated cap sheet to top it all of. All set in cold ap or mastic. The drain ring is fine, they all generally sit a bit above the roof level.

cjthedad 02-10-2012 10:26 AM

I have spent 25 years in the roofing business and in all those years we only had one job where these types of drains were the best option and that was sad because these are not good drains. These drains also do not meet the standards “strainer free area” requirement throughout all the sizes. This may not be an issue for you it depends on how much area you are draining to this drain. They are also very hard to keep watertight. Look at the membrane clamp it is cut at the 90 degree. This is the highest contraction point and it has the least compressive strength. Also look at the bolt areas there is what a total of ¼” of compression. Built-up roofing materials do not like 90 degree bends that is why cant strips exist. It makes a 90 degree in to two 45’s. This is industry standard. Single ply’s will conform to a 90 degree. I am sorry, when it starts to leak it will be right at the 90 degree bend or at one of the bolts and probably at the bolts because it is holding water due to the fact that the drain was installed too high. A properly installed drain has the top of the drain ring/clamping collar level or lower than the surrounding roof membrane. Anything else is not a proper installation. This is why low slope roofing has such a bad reputation the details are done wrong more time than not. Your best option would have been to install a scupper as before but with a round outlet that could be no-hubed to PVC pipe because the downspout was your main problem. So if this turns into a big problem down the road have a good sheet metal company build you a box scupper that will fit into this area with positive slope and have flanges that extend to the top surface around the recessed area with a round outlet to connect to PVC piping. What is the possibility of closing it off and pushing the water off the end of the roof? No picture of that so didn’t know if that was possible. Good Luck

r00ferguy 02-11-2012 09:59 AM

that is the wrong type of scupper for that roof right shape wrong type
2nd thing mastic and paper omg no way leak.
3rd that roofer had no idea what he was doing
4th its a easy job to torch that new drain in get a real roofer in there to do it

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