Use both 4 in ports at the same time on a 2hp dust collector

[Rick Pinzon]

I have a grizzly 2 hp dust collector with a 6in inlet and the plastic wye with two 4in ports. I have bunch of 4in hose that I got from someone else and wondering if any uses both 4in ports at the same time with any success. If so, any suggestions besides upgrading to 6in. I will soon upgrade , just been pricing it out and so I need design and come up with cash to buy all the parts. I figure in the mean time I would use both ports instead of the standard single 4in hose setup. I know it’s not practical, just wondering if anyone as attempted this.

[Josh Kocher]

I used to have a General single stage DC with a splitter like that. I don't think it will work as well as just having a single 4" run. I ended up taking that splitter off and using 6" to a separator, then 4" after that.

[glenn bradley]

I have a 2 hp cyclone with a (reduced to) 6 inch main. I routinely run more than one 4 inch gate open at a time without issue.

[Rick Pinzon]

Thank you for the feedback

[Larry Frank]

So, you have a dust collector and want to run two 4" hoses. You probably will decrease the flow by half compared to using one hose. If that is sufficient for your needs, then it is fine.

[lee cox]

I was at a Woodcraft DC free class a few months ago. What I learned is if you are using a 6 inch main with 4 inch at the tools then it is best to run 2 4 inch open ends rather than 1. You will not get enough flow for the 6 inch main only running 1 4 inch opening.

[Chris Parks]

Using any flex hose kills air flow by large amounts, using two would do that even better.

[Joe A Faulkner]

Will adequately gather chips and larger particles of saw dust. I run two short 4" pipes to my bandsaw. From all that I've read regarding fine dust, most 2 HP configurations don't move enough air.

[Lane Hardy]

Mr Faulkner brings up a very fine point!
what is it you want to do? Remove the chips or or the fine dust that you can not see that does the most damage to your health?
when we look at it that way we most like say both! However if you want to protect your health you need lots of airflow to remove the fine dust. More than what you need to move the chips. Regarding 2 hp that depends on several factors who's
2 HP Harbor Freight? It ain't 2 hp. If it is not good!
what is your Altitude? Air density has a lot do do with how much airflow you need to do the job.
It is a fine balance for dust control between available airflow and air velocity to to evacuate fine dust particles from a machine. Chips not so much of a problem as long as you have adquite velocity to suspend the chips all the way to the collector.
then you have to consider how much air can the blower handle with two gates open?
Lots to consider.

[Mike Cutler]

I'm a little late to the party, but I also use both 4" ports of my Jet DC1100. It's not ideal, and is a definite compromise for dust collection, but it works, sort of okay.

My next major investment has to be some type of a cyclone. But I need one that isn't so tall, due to the low ceilings I have to work with.

[Mike Chalmers]

I was at a Woodcraft DC free class a few months ago. What I learned is if you are using a 6 inch main with 4 inch at the tools then it is best to run 2 4 inch open ends rather than 1. You will not get enough flow for the 6 inch main only running 1 4 inch opening.Don't know what was shown at this class, but I am running a 2hp with 6" mains with one 4" at the tools at a time. I certainly get enough flow to take all chips and dust collected to the SDD.

[Larry Edgerton]

I was at a Woodcraft DC free class a few months ago. What I learned is if you are using a 6 inch main with 4 inch at the tools then it is best to run 2 4 inch open ends rather than 1. You will not get enough flow for the 6 inch main only running 1 4 inch opening.

This. Mine is a lot bigger but I blow outside so I can see how different things affect flow. If I am running say the six inch at the planer I will open up the four at the jointer that is the other side of the last wye before the planer. By doing this I am throwing the sawdust about four feet farther, with no problems at the planer.

On your blower I have no idea, but just saying.........

Also, when I first moved the shop and was temporarily dragging around a 6" long flex hose my planer would clog, all the same other than ducting. Flex definitely cuts flow.

[Mike Chalmers]

This. Mine is a lot bigger but I blow outside so I can see how different things affect flow. If I am running say the six inch at the planer I will open up the four at the jointer that is the other side of the last wye before the planer. By doing this I am throwing the sawdust about four feet farther, with no problems at the planer.

On your blower I have no idea, but just saying.........

Also, when I first moved the shop and was temporarily dragging around a 6" long flex hose my planer would clog, all the same other than ducting. Flex definitely cuts flow. I can only speak to my own situation. I have used an anemometer to measure air flow with one 4" port open, and with two 4" ports open. Both, of course, using the 6" mains. More air flow with just one open than with two. I have no build up of chips or dust of any kind in my system. These are facts, not speculation or theory, however, I have observed only my own system.

[Roy Petersen]

I can only speak to my own situation. I have used an anemometer to measure air flow with one 4" port open, and with two 4" ports open. Both, of course, using the 6" mains. More air flow with just one open than with two.
That would be a measure of speed, not volume, wouldn't it? Any time you narrow an opening it will increase velocity, but the amount of air moving through it will not increase. From what I've been reading, it's not the speed as much as it's the combination of speed and the amount (volume) of air that keeps things suspended and moving. If there's not enough to keep it suspended in the airstream, it can drop out and create eddies and be far less efficient at keeping the fine stuff moving along. Anything not moving will create drag and slow things further, though it may not be evident at the port until it's severe.

[Larry Edgerton]

I can only speak to my own situation. I have used an anemometer to measure air flow with one 4" port open, and with two 4" ports open. Both, of course, using the 6" mains. More air flow with just one open than with two. I have no build up of chips or dust of any kind in my system. These are facts, not speculation or theory, however, I have observed only my own system.


You will have more air flow at the opening of the 4", but less at the exit of the 6".

[Larry Frank]

I find some of the assertions in this thread interesting.

If you have one 4" port open at a machine, you will get a certain flow at the machine. If you open a second 4" port, the overall flow through the dust collector will increase but the flow at your machine will decrease. What is important is the flow at the machine that you are using. Of course if your machine is not very powerful and you are running 6" ducts, you may need to open a second port to increase speed in the 6" pipe to have sufficient air flow to keep dust and chips moving.

The other point is that it is only necessary to increase the port size on your machine if you do have sufficient air flow because of your dust collector. With my dust collector, I get about 900 cfm through one open 4" blast gate on my system. This is more than enough for good dust collection. If I open a second 4" blast gate, I get about 1300 cfm but the flow from the first blast gate goes down slightly. If I open a single 6" blast gate, I get about 1500 cfm. Note: I am running a 5 hp Oneida Super Dust Gorilla. With this machine, the 4" ports on my machines work fine. However, with a smaller machine such as the HF, this may not be the case. It important to take all of the advice and try to analyze it as it applies to your machine, duct work and your requirements.

I did not use a fan anemometer to get the above numbers but measured the static pressure and used the performance curve that I had previously developed using a hot wire anemometer and a digital pressure gauge.

[Mike Chalmers]

That would be a measure of speed, not volume, wouldn't it? Any time you narrow an opening it will increase velocity, but the amount of air moving through it will not increase. From what I've been reading, it's not the speed as much as it's the combination of speed and the amount (volume) of air that keeps things suspended and moving. If there's not enough to keep it suspended in the airstream, it can drop out and create eddies and be far less efficient at keeping the fine stuff moving along. Anything not moving will create drag and slow things further, though it may not be evident at the port until it's severe.While what you say is true, it is also not relevant to the point I am making. The premise was that two 4" ports are open, but only one is actually in use. In that situation, it is obvious that more FPM is going to yield more CFM.

[Mike Chalmers]

I find some of the assertions in this thread interesting.

If you have one 4" port open at a machine, you will get a certain flow at the machine. If you open a second 4" port, the overall flow through the dust collector will increase but the flow at your machine will decrease. What is important is the flow at the machine that you are using. Of course if your machine is not very powerful and you are running 6" ducts, you may need to open a second port to increase speed in the 6" pipe to have sufficient air flow to keep dust and chips moving.

The other point is that it is only necessary to increase the port size on your machine if you do have sufficient air flow because of your dust collector. With my dust collector, I get about 900 cfm through one open 4" blast gate on my system. This is more than enough for good dust collection. If I open a second 4" blast gate, I get about 1300 cfm but the flow from the first blast gate goes down slightly. If I open a single 6" blast gate, I get about 1500 cfm. Note: I am running a 5 hp Oneida Super Dust Gorilla. With this machine, the 4" ports on my machines work fine. However, with a smaller machine such as the HF, this may not be the case. It important to take all of the advice and try to analyze it as it applies to your machine, duct work and your requirements.

I did not use a fan anemometer to get the above numbers but measured the static pressure and used the performance curve that I had previously developed using a hot wire anemometer and a digital pressure gauge.What he said.

[Mike Chalmers]

You will have more air flow at the opening of the 4", but less at the exit of the 6".Yet no dust or chips in the mains.