Spray bar hole size and spacing

[Southern Fist]

Can someone give me a suggestion on hole size and spacing for a diy spraybar? I’m running an fx4 on a 75 gallon tank. I’m going to have plants, apistos angels and tetras in it.
I’ve made one attempt with 1/4” holes 1” apart, and it seems like there isn’t enough flow. Bar is 3/4” pvc (1” in reality) and about 42” long.
thanak
Ridley

 

[FFGuest6357]

I would invest in a step drill bit...

you could take that same bar and use the bit to gradually increase hole size until you get your desired flow.

I haven’t figured out how to link webpages on this forum from my phone, but a quick google search will show you the drill bit I’m talking about, it basically allows you to gradually increase the size of the hole without switching bits and trying to center your hole.

most of them are made for drilling metal, so you would have no problem drilling pvc.

 

[mcordelia]

another thing to bear in mind is that with a 42'' long pipe, the flow at the "beginning" of the pipe will be more than the flow at the "end" of the pipe, both due to lost water but also somewhat due to drag. If you want the same volume of water coming out at each part, start with smaller holes at the beginning and larger holes at the end. If you want the same force of water coming out at each part, then I think(?) you start with larger holes at the beginning and smaller holes at the end, however you then have to consider blockage effects and it gets all screwed up. You'd have to talk to someone who has a fluid dynamics degree to get it totally right, but worth considering using maybe 3 different hole sizes if you want to standardize your flow over the length of the bar.

 

[FFGuest6357]

And if @mcordelia is right, a step drill bit would be useful in the fact that you can use the same bit to drill all the holes to your desired size.

pvc is also a relatively cheap material, so it wouldn’t hurt buying some extra pieces and experimenting with different setups.

The pvc spray bar should also probably be submerged below the water line, there for no need to glue the joints inside the tank. You could easily swap experimental spray bars in and out to find the right flow.

If there’s nothing in the tank yet, you could experiment with adding food safe colouring to the tank to visually see the flow. I have had people suggest that to me before. I’m sure someone else here could have more insight on that though, and I would do it before you add too many scaping objects, don’t want it to stain...

 

[mcordelia]

another way to test for flow (only out of the spray bar, not within the tank) is to just have it spraying into air at the same position/angle that it would be spraying into the tank, and you can either visually or by collecting the output into containers measure how much is coming out at which part. This is of course going to decrease if you submerge it, but if you submerge it horizontally the effect of the water pressure against it will at least be uniform. If you need to measure the effect of the water pressure against it and you are submerging it such that one end is higher than the other, then the food coloring trick is probably the only way to measure that.

 

[Colin_T]

2mm diameter holes (1/4 inch is 6mm and that's too big).
have holes about 1 inch apart, which you already do.
shorten the length of the spray bar if it's still too weak. most spray bars are about 12-18 inches long, not 42 inches.

 

[Southern Fist]

Thanks everyone.

I just tried a second spraybar, using smaller holes every 2” (total length about 36”) and I think I have too much flow. I’m going to have some angelfish in here, do I need to reduce flow significantly, a little bit, or very significantly? My guess is that I should enlarge the holes one size, instead of adding holes. Any advice?

https://share.icloud.com/photos/0y4pCdRJfnGALBqTQr2EvMIbw

Ridley

 

[mcordelia]

So the 42" with 1/4in holes did not give you enough flow, but the 36" with smaller holes gave you too much flow right? And by "flow" we mean speed/force of water coming out right?

If the question is do you add more holes of the same size or make the current holes bigger, it's a "6 of one half dozen of the other" kind of problem without sitting down and doing the math for it. If you go with more holes, I think you might be slightly more likely to end up in a scenario where the water comes out more forcefully at the beginning of the bar and less at the end of the bar, but I don't know by how much. Maybe start by enlarging the holes at the end first and go from there? Maybe do two holes to start with and then test, etc

 

[Southern Fist]

2mm diameter holes (1/4 inch is 6mm and that's too big).
have holes about 1 inch apart, which you already do.
shorten the length of the spray bar if it's still too weak. most spray bars are about 12-18 inches long, not 42 inches.

So the 42" with 1/4in holes did not give you enough flow, but the 36" with smaller holes gave you too much flow right? And by "flow" we mean speed/force of water coming out right?

If the question is do you add more holes of the same size or make the current holes bigger, it's a "6 of one half dozen of the other" kind of problem without sitting down and doing the math for it. If you go with more holes, I think you might be slightly more likely to end up in a scenario where the water comes out more forcefully at the beginning of the bar and less at the end of the bar, but I don't know by how much. Maybe start by enlarging the holes at the end first and go from there? Maybe do two holes to start with and then test, etc

Thank you , I ended up going up to 1/4" holes, every 2 inches on the 36" long bar. It seems to be just right - Will know when I get some fish in there tomorrow.

 

[porl66]

1/4" holes seems VERY large. Thats a 6mm hole. I checked the holes in my spray bar and they are 2mm maximum

 

[Southern Fist]

Well, all i can say is all of my plants throughout are gently waving around now. with the 3/16" holes, some seemed to be blowing around too hard. Its an fx4 filter, so its a decent sized filter.
ridley

 

[663]

Can someone give me a suggestion on hole size and spacing for a diy spraybar? I’m running an fx4 on a 75 gallon tank. I’m going to have plants, apistos angels and tetras in it.
I’ve made one attempt with 1/4” holes 1” apart, and it seems like there isn’t enough flow. Bar is 3/4” pvc (1” in reality) and about 42” long.
thanak
Ridley

Is there a direct indication that your spray bar isn't keeping up with the optimal flow of your filters pump? One easy way to get a measure of flow is to position the spray bar above the water line. While this configuration helps with aeration, it will also give you an audio feel of exhaust strength.

Before I popped for my current workhorse filter, I reviewed the hell out of it. 2 reviews suggested that I modify the pre-filter (which acts as a carbon foam intake for the entire filter) that acts like a reverse flow spray bar. When I tried to drill the tube I quickly learned that it wouldn't be an easy mod without using a vice to secure the tube. I left the unit as shipped, and performance is what I'd hoped.

 

[Southern Fist]

Heres my exposed jets. Surely this is enough pressure?

 

[663]

Heres my exposed jets. Surely this is enough pressure?

It looks muscular enough to me. How's water column movement in general?