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Community and Q&A

Downspout filter

user-5946022 | Posted in Green Products and Materials on

What is the general consensus on the best type of downspout filter?

I presume the type of roof onto which the water is falling, the presence (or absence) of gutter guards, destination of the water, and intended use of the water would all have an impact on the response.

I see basic home center type “filters” for $6, such as:
These are advertised as “self cleaning” however my experience is wet leaves can easily get stuck on the grate resulting in the water diverting out the chute, and not going to its intended destination.

On the other end are $130 (or more) items such as: with which I have no experience.

There are many in between, both in function and price point.  What should I be looking for, and which brands have worked well for others?

Specifically, I’m wondering about the best type of downspout filter for
– Roof: Asphalt shingles
– Gutter guards: What is the recommendation?  See also below.
– Destination & Use: Two destinations
a:Underground Flow Well set in #57 stone, with silt control fabric between the stone and the earth.  Water is supposed to perk back into the earth.  Theoretically keeping as much debris as possible out of the flow well and surrounding stone will retain it’s original capacity longer.
b: One downspout will divert to a rainwater holding tank to be used for irrigation.  Overflow from the tank will divert back to the FlowWell. I presume the filtration for this system needs to be more robust?

In my area, people just slam these rainwater systems in to meet code and pass inspection, and most of them lose capacity very quickly.  I’d like to be environmentally responsible and keep my stormwater out of the city system as much as possible, so I’d like to maintain the capacity of my system as long as possible.

Gutter guards seem like the first “prefilter” for these systems, so having the correct type seems critical.  What is the recommendation on that?
– The very fine mesh stainless steel guards will filter out the fines, but there are claims pollen clogs the mesh, so while what gets in is well filtered, the clogged mesh allows some/most of the water to roll over the gutters.  Claims are similar for the foam inserts.
– The larger mesh (approx. 1/4″ size openings) are claimed to be more resistant to clogging.  Are these the best to use along with a fine mesh downspout filter?  The downspout filter at grade is obviously easier to clean.

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  1. Expert Member
    BILL WICHERS | | #1

    All of these are clots waiting to happen. Gutter guards are the best options, and there are only a few systems that work without needing constant attention. The level of maintenance is dependent primarily on what kind of tree debris gets into the system (oak leaves are heavy, for example, and tend to “glue” to surfaces).

    The only gutter guards I find work well are the kind that look like rigid metal panels on top of the gutters. Debris mostly goes over the side, while water drops through into the gutters.

    I wouldn’t worry about fine sand-like debris from the shingles. Water velocity sufficient to knock that loose will probably also be sufficient to prevent buildup of the fines in the piping.

    I don’t like any of the filters that go in the downspouts. These types of filters are catching debris that should have been filtered out in earlier stages, IMO.


  2. user-5946022 | | #2

    Thanks Bill. Gutter guards as the first filter makes the most sense to me also. Just need to figure out which kind is best.
    As for the downspout filters, they are required by code in my area, so I have to figure out which one to use.

  3. aaronbeckworth | | #3

    C L,

    I’ve seen a couple of impressive rainwater harvesting systems here in SW New Mexico that include “first flush” tanks, which are simply small tanks that first fill before allowing overflow on to the main storage tank, cistern, etc. In our dry climate the intent is utilize the captured rainwater, so some sort of storage is involved. The “first flush” tank captures debris, much like a sand separator for a well. However, leaves and floating debris must be kept out with gutter guards or some other device.

    Good luck!

  4. Expert Member
    Peter Yost | | #4

    At my house, I am in the gutter guard...

    While some systems are better than others, never found one that does not involve me...


    PS - from southern VT with a slate roof where gutters are most often an annual installation cost...

  5. Expert Member
    Akos | | #5

    I've found gutters with the large mesh filter to build up with the granules from shingles. No experience with the fine mesh. My current place has the perforated metal ones. Definitely keeps all leaf debris out (mostly oak/maple here), can't comment on granules though as I have a metal roof.

    That German downspout filter looks pretty neat. One thing might be worth while to look at is a first flush diverter. These are simple/no maintenance.

  6. Expert Member
    Peter Engle | | #6

    For roof water that is going into a dry well or that will be used for irrigation, there's not much need for a first-flush filter. Those are really more for water going into a cistern for eventual drinking water.

    I find that the "gutter helmet" style gutter guards work pretty well to keep big debris out of the gutters. However, they may behave badly in ice-prone regions. I am in coastal zone 4, so not much long-term ice/snow here. If you have decent gutter guards, downspout filters are probably unnecessary. If your local code requires them, go with the cheap ones to satisfy the code guys. The mineral granules from the shingles will take forever to clog a dry well or cistern.

    I have done inspections of dry wells used for roof drainage. The inspections are required in some places around me every 10 years as part of the permitting process. I've mostly found that the small amount of organic debris that finds its way into the dry well composts in place pretty effectively. So much so that the stone in the wells has been clean even after 20 years in some cases.

    Unless you've got lots of big trees (especially evergreens) hanging over your house, my feeling is: Use decent gutter guards, with a coarse downspout filter as a backup. Don't worry about the fines too much.

  7. user-5946022 | | #7

    Does anyone have any experience with the fine mesh type gutter guards? Sounds like those might be the best?

    Also, any experience with specific downspout filters is appreciated as there is one area that can't have gutter guards, so the downspout filter will be the only filter.

    1. Expert Member
      MALCOLM TAYLOR | | #8

      CL, I've used these and they work well.

    2. Expert Member
      BILL WICHERS | | #9

      If you’re talking about the gutter guards that actually go on the gutters, the rigid panel type tend to work best. The roll stuff doesn’t, and anything that makes a “hump” after you install it will tend to accumulate debris against the roof edge which is a bad thing. You want a flat panel at a slope going down towards the edge. You want water to fall through into the gutter, but debris to go over the edge.

      I saw one gutter guard that looked like lots of very closely spaced slats (something like one side of an A coil for an air conditioner) at a trade show a few years ago, but I can’t find the info now. It looked like it would work really well.

      If you’re asking about downspout debris filters, I don’t use those myself.


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