PVC vs acrylic pipe dimensions

[Forestwalker101]

So Im planning a diy air stone skimmer and I was comparing acrylic vs pvc pipe for the body. Sch 40 pvc is 6.625" OD for 6" pipe. Acrylic pipe is 6" OD, at least what ive found online. My concern is that pvc fittings wont work with acrylic pipe.

Anyone used acrylic pipe with pvc fittings likr this have any issues with dimensional differences?

 

[José Morales]

So Im planning a diy air stone skimmer and I was comparing acrylic vs pvc pipe for the body. Sch 40 pvc is 6.625" OD for 6" pipe. Acrylic pipe is 6" OD, at least what ive found online. My concern is that pvc fittings wont work with acrylic pipe.

Anyone used acrylic pipe with pvc fittings likr this have any issues with dimensional differences?

Ah man.. I wouldn't diy a skimmer, it's your systems most important filtration, don't go cheap on that..

 

[mfinn]

So Im planning a diy air stone skimmer and I was comparing acrylic vs pvc pipe for the body. Sch 40 pvc is 6.625" OD for 6" pipe. Acrylic pipe is 6" OD, at least what ive found online. My concern is that pvc fittings wont work with acrylic pipe.

I think you answered your own question. You measured the pvc and acrylic tube you found online and they don't match up.
If it were me, I would contact a couple of the online acrylic tube sellers and ask if they have any tube that would work with pvc fittings.

 

[Bradw18]

Many many successfully diy skimmers out there and many plans for them as well. go for it!!!!!

 

[Andnosobabin]

Ah man.. I wouldn't diy a skimmer, it's your systems most important filtration, don't go cheap on that..

More the reason to build your own. Most skimmer mfgs seem to miss an important part of a successful skimmer and that's contact time with the water and bubbles being 2 min or longer. Maybe I don't know all the engineering on them but it would seem something as short as your normal skimmer falls very short of this considering the books I've seen cited state a skimmer height should be four to five feet optimally.
I'd say not to worry so much about the clear acrylic and actually do some delving into dimensions and go with straight PVC but on a system that's actually based on your tank design not some prepackaged box.

 

[Andnosobabin]

So Im planning a diy air stone skimmer and I was comparing acrylic vs pvc pipe for the body. Sch 40 pvc is 6.625" OD for 6" pipe. Acrylic pipe is 6" OD, at least what ive found online. My concern is that pvc fittings wont work with acrylic pipe.

Anyone used acrylic pipe with pvc fittings likr this have any issues with dimensional differences?

You can buy clear pvc (expensive as it's pharmaceutical grade) from www.usplastic.com

 

[Skydvr]

It is the bombardment rate (number of times a clean air bubble contacts water molecules. Related to dwell time, but not necessarily dependant on dwell time) and air bubble column diameter that are critical. There are many factors that affect the bombardment rate. Flow rate through the skimmer, turbulance, height of the skimmer, diameter of the skimmer, velocity, flow rate, and size of the bubbles. Those will effect other factors of how efficiently the skimmer works as well.

You can go with a shorter skimmer with a wider diameter, moderate flow rate, and a wide dense column of fine air bubbles and get a significant dwell time and a high bombardment rate. Of course taller makes it a little bit easier, but taller isn't necessarily more efficient or effective if it does not increase the bombardment rate. I started reading through Aquatic Systems Engineering again and there are a couple chapters (short and concise) on skimmers that explain ideal designs and how to calculate what size tubing and flowrate to use to accomplish the rate of skimming you desire and how to couple that with available space (max allowable height with room to remove the collection cup, etc). I am sure you can find plently of the info online a well. Or just go for it and make what you think feels appropriate. An air driven counter current skimmer is fairly inexpensive and simple to design (they are also really efficient). If it isn't as effective as you hoped, add more or finer bubbles, maybe add a second column. If you are severely limited on height, you could build two series skimmer chambers (daisy chain them) where the first feeds into the second.

 

[Skydvr]

The problem is that you are trying to mix tubing and pipe (the terms are not interchangeable).

The answer seems kind of convoluted at first because the standards for pipe results in slightly differing ID and OD.

Tubing is structural and has a precice OD. Acrylic is typically tubing (any hollow shape other than round is tubing, not pipe, as square/rectangular is not really suitable for transporting fluids/gasses/etc and is impractical for longer runs of more than one section). There is clear PVC pipe that conforms to the schedule and nominal diameter system of standard pipes.

Pipe is designed for flow and is based on a nominal diameter that results in approximately the givin diameter as an ID depending on schedule (wall thickness). It gets confusing as a given schedule pipe has different wall thicknesses based on the Nominal Pipe Size (NPS). The OD of the pipe is determined by the NPS and pipe schedule (i.e. 2" Schedule 40). It plays into weight and pressures (but allowable pressures are not determined strictly on pipe wall thickness and material of construction). Like I said, not exactly straight forward.

The ID varies slightly due to schedule, as does OD. But the OD is fixed for a given schedule and nominal pipe size to allow for a standardization of fitting and couplers. The difference in OD for different schedules is to intentionally prevent mixing fittings of different schedules resulting in a weaker fitting on a higher pressure system.

There is a pretty good description on Engineering Toolbox. Probably better than what I tried to eXplain above.

 

[Andnosobabin]

It is the bombardment rate (number of times a clean air bubble contacts water molecules. Related to dwell time, but not necessarily dependant on dwell time) and air bubble column diameter that are critical. There are many factors that affect the bombardment rate. Flow rate through the skimmer, turbulance, height of the skimmer, diameter of the skimmer, velocity, flow rate, and size of the bubbles. Those will effect other factors of how efficiently the skimmer works as well.

You can go with a shorter skimmer with a wider diameter, moderate flow rate, and a wide dense column of fine air bubbles and get a significant dwell time and a high bombardment rate. Of course taller makes it a little bit easier, but taller isn't necessarily more efficient or effective if it does not increase the bombardment rate. I started reading through Aquatic Systems Engineering again and there are a couple chapters (short and concise) on skimmers that explain ideal designs and how to calculate what size tubing and flowrate to use to accomplish the rate of skimming you desire and how to couple that with available space (max allowable height with room to remove the collection cup, etc). I am sure you can find plently of the info online a well. Or just go for it and make what you think feels appropriate. An air driven counter current skimmer is fairly inexpensive and simple to design (they are also really efficient). If it isn't as effective as you hoped, add more or finer bubbles, maybe add a second column. If you are severely limited on height, you could build two series skimmer chambers (daisy chain them) where the first feeds into the second.

I wish I had that book on hand the best info I found containing excerpts from ASE didn't say anything more than dwell time nothing about bombardment rate. It did mention optimal width and height but that's it.

Let me try to understand is it the increased velocity in the shorter brand name skimmers that increases bombardment rate and dwell time? Or are there other factors in play and how would one best diy this?

 

[Skydvr]

Trying to not drail the pipe and tubing question too much further.

They are not as efficient, but can make up for that with a larger diameter as well as with a higher flowrate and turnover if they are sized large enough.

A counter current skimmer can be narrower in diameter, to a point, and doesn't need to sit in the sump, so it can be tucked into areas that are out of the way or sit in the space between the stand and wall on tanks that are plumbed from behind. There is a size scale where eventually the in sump venturi skimmer wins out if you want/need to keep the equipment concealed in the stand.

You should see if your local library can get the book through an exchange if you can't find it yourself. He does promote a couple of his products in one of the chapters (which I am not sure are actually available anymore anyhow), but the principals are still pretty solid and applicable to other manufacturers. He kind of handwaves some things and simplifies some of the equations, but the book isn't intended as a college textbook and most of the calculations don't need to be that precice.

 

[red13]

I've glued acrylic tubing to pvc fittings at work. Use alot of thick glue (we use Weld-On), and make a jig to keep the acrylic straight in the fitting. Let the glue dry overnight. The glue will fill in the gap. I wouldn't do it for a high pressure line, but for a skimmer I think you should be fine.

 

[AlexG]

Rather than using acrylic use UV thin wall PVC since it fits schedule 40 fittings and it is clear. I just checked 6" and it costs $33.35 per foot at https://flexpvc.com/cart/agora.cgi?product=PVC-CLEAR-PIPE-UV-Thinwall . I used the thin wall UV PVC for my skimmer and it has worked out great. I have made several DIY skimmers and they have all worked out great. The difficulty with fitting acrylic to PVC is that special glues are needed and fittings might not make a good fit making it difficult to glue them. It can be done but I would suggest going all PVC if you can.