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I have a glass house that encloses an above-ground pool. For gutters, they have used some silly system, where at the joint, the flow is restricted to a third of its capacity.

It has a downpipe on each side of the glasshouse, but because of the restrictor bracket, not enough water escapes down it. So I was planning on putting in a brass fitting on each of the six sections, with a pipe to drain it to the ground.

It is not a normal gutter and is painted to match the aluminium of the glass house, so I can't replace it easily.

I have never used a hole saw on PVC and I am afraid of cracking it. It's a 30 mm hole. How can I ensure that I don’t crack it? I can’t take the gutter down, so I have to work on a ladder.

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    Can you post a picture of what you want to cut a hole into? That may help provide suggestions for how to make the hole or drill it accurately.
    – Freiheit
    Commented Jun 30, 2023 at 14:22
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    PVC what? Thickness and shape matter. PVC does tend to explode under stress.
    – isherwood
    Commented Jun 30, 2023 at 15:27
  • Three excellent answers, and I can't pick one of them to tick :-) Commented Jul 1, 2023 at 12:26
  • @Freiheit, I would have posted a photo already, but the weather has not been too good. Commented Jul 1, 2023 at 12:26

8 Answers 8

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In general, yes, a hole saw can certainly be used on PVC.

In specific, becoming brittle from UV exposure as mentioned in @KMJ's answer would be my biggest worry in drilling these things. Old plastic loves to crack.

I think applying heat to soften the PVC might be a way to address that concern - either hot water (near-boiling) or a heat gun - limit application to the point where it softens a bit in the hole area, don't overdo it and distort the whole thing.

I'd also take the time to clamp a board with a hole-saw drilled hole on the side you will drill from, and another board to the other side to sandwich the place you'll be drilling.

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  • Nice tip on the boards. I didn't even think of that, despite having used the technique before to cleanly drill thin materials.
    – KMJ
    Commented Jun 28, 2023 at 23:01
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    Sandwich between boards may bot be an option the gutter is curved instead of boxed (use duct-tape as Ruskes suggested in that case). But warming it (heat gun on low setting, you don't want to deform, melt or scorch it) to reduce brittleness is a very good idea. I've used that myself a couple of times with good success.
    – Tonny
    Commented Jun 29, 2023 at 8:52
  • +1 for the boards. Even if curved you may be able to rig something to support the PVC. Even a pool noodle wrapped in layers of card and duct tape would be better than nothing, Then strap it round with more duct tape, tight, over where you're drilling.You'll be going slow so snagging is only a minor worry. Better than card would be plastic sheet material just flexible enough to bend into shape - like an offcut of guttering or (split) downpipe
    – Chris H
    Commented Jun 30, 2023 at 8:25
  • Less so up a ladder, but I like to use my wheel bracer (egg-beater hand drill) for sheet plastic. It's gentle and you can feel what's going on.
    – Chris H
    Commented Jun 30, 2023 at 8:27
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Most important is do not force it. Let the saw do its job.

Reduce the speed to slow to reduce forces.

The choice of the saw teeth is important. Too small will clog up fast. Too rough will chip it.

Additional chipping/cracking prevention tip:

Cut a 2x2 inch or larger duck tape, and stick it where the hole should go, and now drill through it.

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    Good tip on the tape - even painters tape can help prevent chipping or cracking.
    – KMJ
    Commented Jun 28, 2023 at 23:00
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    Also, if the hole saw has teeth, consider running it in reverse for the first part of the cut. Less chance of it running away across the surface.
    – PeteCon
    Commented Jun 29, 2023 at 18:39
  • @Nelson I have a personal spellchecker :)
    – Traveler
    Commented Jul 22, 2023 at 5:42
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Go slow! Your enemies here are going to be pressure and heat. Use your drill at relatively low speed. Use a very sharp hole saw. Drill a little bit of the hole, then check to see how warm the PVC is getting, then drill a bit more if it's still reasonably cool. Don't press too hard or you'll risk cracking the PVC. Fair warning: if it's been out in the sun for more than a season or two, it's likely to be fairly brittle and you'll have a risk of cracking them anyway. If you have a piece you can easily replace, you might want to get a replacement for it, replace it, then experiment on the piece you replaced before you dive in to the project. Usually PVC gutters just clip in to the connectors, so they're pretty easy to replace portions of unless they used the style of brackets that drill through the gutter.

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Alternatively, use a step drill. I have found them to work very well on plastic, especially plastic that is prone to cracking.

Either way (hole saw or step drill), I'd practice on a scrap of PVC first to get a feel for it.

enter image description here

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    Great idea for smaller holes, but downpipe tends to be 50, 60, 65, or 75mm and I've not seen a step bit that large. Do they exist in larger sizes ?
    – Criggie
    Commented Jul 1, 2023 at 1:07
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Your last resort is any kind of toothed bit, be it a twist bit, holesaw, step bit, etc.

While most any drill bit will cut most any plastics, for your application I'd use an abrasive holesaw such as one for drilling holes in shower tiles, and would go to the point of buying a new one before using any toothed bit that I might already happen to have.

Personally, though, if I didn't have an abrasive hole saw on hand, then even before going to the store, I'd take a short length of non-galvanized metal tube (for example electrical conduit, copper pipe, etc) say 2' long, heat one end over a flame (propane torch, gas stove, etc) and use it melt the holes.

Third in line would be to score out a plug using an old spade bit ground to have longer spurs.

Fourth in line would be to put the drill in reverse and use a toothed holesaw.

Yet another option is initiate and enlarge the holes using an abrasive bit in a small rotary tool such as a dremel, or even a standard drill.

Another approach alltogether is to first use PVC cleaner and glue to permanently attach a stub, say 1" long, of your downspout pipe as your eventual outlet pipe, then drill out the gutter through that. Glue a coupler to your pvc downspout. Paint your PVC to avoid UV degradation.

Lastly, if you do end up with a blooper, it can be repaired with a couple of skim coats of PVC glue in the inside, after using some cleaner on the area.

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Drill your pilot hole as normal. Place the drill in reverse and proceed to drill your hole.

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    Whats the reasoning behind drilling in reverse? Commented Jun 30, 2023 at 20:19
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    @RohitGupta starting in reverse allows the the points/tips of the saw part to scratch a channel initially. This will eliminate the point's ability to dig into the PVC, catch, and cause a crack. Downside doing the whole hole backward will take a long time. I'd try backward for long-enough to make a channel and then switch to forward with minimal down-pressure.
    – Criggie
    Commented Jul 1, 2023 at 1:06
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A backing board would be a wise idea, to limit the flex available to the PVC. However you're talking about a gutter which is likely a curved surface. And it is likely you'll be drilling up from below rather than pushing down from above.

Also you're working at height already, so there's an added risk factor.

I would consider a hot knife for making a calm, relaxed hole in PVC. I have one for a butane soldering iron. Note, this will stink so consider the wind direction. Ideally work on a windless day to help keep the heat in the blade.

If the gutter has a flat bottom you might get away with

enter image description here

else you will need to find a curved dropper adapter like

enter image description here

These are intended to be pushed in from above through your hole, and sealed all the way around the edge with an adhesive sealant or PVC welding cement like this:

enter image description here

Note that PVC gets very soft when heated - it can be handy to have a spray bottle of water to instantly harden floppy parts.

Also be aware that white PVC scorches easily. Don't overheat it else there will be brown patches.


The other option is to identify the profile of the existing guttering and see if its available for purchase. If so, buy some dropper fittings and some joiners and a tube of PVC sealant. Slice out the section you don't want, and attach the dropper section with the same adhesive sealant cement.

enter image description here

Remember, its a water gutter so it just has to be sealed, and to look okay from the ground. PVC guttering lasts several decades in normal usage and even then only breaks when you start manipulating it.

Your last option is a complete replacement of all the guttering with new PVC. This may feel like overkill, but its a valid option and you get to re-do where the downspouts are and how the gutter's fall is organised around the structure. New guttering is a lot of preparation, and then CLICK-CLICK Boom it's done - just like painting, its all in the prep work.

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Cutting should be fine I've leaned ladders against 50 year old PVC gutters never seen any cracking - they seem tought like new, or almost so. Architectural plastic is not the same stuff as they make disposable appliances from.

Hole saw, sure that will work, hot knife, nibbler, or aviation snips are other options. With a hole saw you need to take care not to jam the hole saw, as this is always a risk when cutting sheet products.

brass fittings, yeah if you really want. PVC spout connectors may be available, and will probably be lower maintenance.

I have in the past mis-used a flared funnel-shaped PVC floor escutcheon to connect 40mm PVC DVW pipe to a small gutter.

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