google-site-verification: google634e99ea8d142f7a.html ',' '); } ?>
Norwalk CT 203 858 0080 / Pittsburgh PA 203 858 0080 / Longview TX 903 -291-0848
Select Page

Flat Roof Drains and Strainers on Commercial Roofs

Flat roof drains and strainers are the most important components of any commercial flat roof. They are responsible for properly draining any and all accumulated precipitation. To preserve the life of the roof, however, the debris that collects around them, must be removed on a regular basis. There are several ideas you can implement to improve the effectiveness of a drain system.

The video below shows how a large metal strainer is more effective than a smaller, dome shaped, plastic strainer.

Video Transcript - for Improving your Flat Roof Drainage System

Hi, my name is Erik with Commercial Roof USA.

Strainers are too Small 

A very common issue on flat roofs are the drains. Now, there’s many problems with drains but a very common one that we see all the time is having too small of a drain. They install these and then put on these tiny strainers that are like high but very, you know, small in circumference and the problem is especially in a area with a lot of trees around. Like this one is that just a few leaves clog it up.

As you can see when they wash up, up against it, it creates a high barrier so this roof, this particular one fills up quite deep. So like if you’re not up here every, every couple of days, every couple of weeks especially in the fall, these are constantly clogging up. So, the way we solve this problem is by, first of all, making the drain a little bit lower and we’ll show you that in just a minute, but replacing strainers like this these small strainers with much wider strainers cause like just a few leaves clogging up uh coming up here and clog this up.

Custom-Made Strainers

What we do is custom make a nice wide low strainer like this one. After we lower the drain this will be very good cause just a few leaves stay way out here. You have a lot more space for all the uh, for all the water to come in still. If they wash up over top, the water can still get through. So, small you know, small circular ones like that, they just don’t work.

Lowering the Roof

This is how we solve the issue. First of all, number one, lowering the drain slightly and number 2 putting a much wider, lower strainer on top. Alright I’ve lowered the drain here and um, this is the old strainer. If you remember how small it is just a few leaves and twigs and what not can block this up really quickly. So we’re getting rid of this and you can see how we lowered it a bit and we made it just the right shape for our custom drain here.

Water Flows Freely

Now, this fits in perfectly right here and when a leaf or leaves come in here and start blocking this up, the water then just flows over the leaves onto this, and this thing will block up much less than that. This will take weeks to block up where that can go for like a day. So, um, this is how you do, this is an effective strainer especially when you lower the drain like this and this fits in perfectly. This is the type of strainer you should have on your roof.

Improve Your Commercial Flat Roof’s Drainage System

Improve your commercial flat roof’s drainage system by replacing the small plastic or metal strainers with a customized strainer made from metal. Plastic strainers tend to deteriorate and break from harmful UV rays. Also, the holes and slots of both metal and plastic strainers are too small and narrow, preventing small debris from flowing through to reach the drain. If these types of strainers are not maintained regularly, the buildup of small debris around them will eventually block the flow of water, causing the area to pond. Ponded water can promote the growth of moss and other plant life. Also, leaks are likely to spring from these ponded areas.

Make a Custom Drain Strainer

Make a custom metal drain strainer to improve your drainage system and preserve the life of your commercial flat roof. In the video above, there is an example of the type of strainer we have made to improve water flow even when there is a build up of debris.

Flat Roof Drains and Strainers - This customized drain strainer improves drainage systems and the life of the roof.

Notice the cracks on this plastic strainer. Eventually, the strainer will develop more cracks, then break apart, and become ineffective.

Flat Roof Drains and Strainers - Notice the cracks on this plastic strainer. Eventually, the strainer will develop more cracks, then break apart, and become ineffective.

Lowering a Drain

Lowering a drain will improve drainage from your commercial flat roof. A professional roofer will remove a section of the drain pipe from below the roof, to shorten it. The drain and roof, will then, be reattached to the shortened drain pipe. This is, by far, the best way to remove pooling water from a drain area.

Considerations Before Lowering a Commercial Roof Drain

  • What is the current type of roofing membrane?
  • What other roofing membranes are under the current one?
  • What type of drain is installed? (plastic, copper, aluminum or cast iron.)
  • Are both a plumber and carpenter needed, or can a roofer do all the required work?

The cost of lowering a drain can be as low as $1200 and cost as much $2500.

This video shows how a drain can be lowered to improve drainage.

A Lowered Drain Will Work – Watch Video

Lowering a drain will work. We have lowered drains for over 20 years. A drain that we installed about 10 years ago, shows that even though debris was not removed on a regular basis, the drain still functioned as was intended.


The image below shows how debris can block a strainer. The muddy water pooled and weakened the rubber membrane seals which caused leaks.  

Debris around a strainer and drain will eventually clog drains up

Drain and strainers on a flat roof

 We benefit on Google if you write a comment on Flat Roof Drains and Strainers.

Use “flat roof”  or “flat roof drain” as keywords in your comment. Thanks a lot.

1 Comment

  1. ChristaJuicy

    Hello. I see that you don’t update your page too often. I know that
    writing content is boring and time consuming. But did you know that there is a tool that allows you to
    create new posts using existing content (from article directories or other pages from your niche)?
    And it does it very well. The new posts are high quality and
    pass the copyscape test. You should try miftolo’s tools


Submit a Comment

Your email address will not be published. Required fields are marked *