Acrylic fabrication questions? I can help!

40 does 'bite' into acrylic (dissolves it), it's not just a glue.epoxy. As far as it biting into PVC I don't know from experience. But as for bod quality, this has mostly to do with the operator (i.e. a joint is only as good as you prepare it to be).

Perhaps my attempt at welding PVC to acrylic with 16 was not done correctly. I only tried it once (and did not rough up the PVC surface) but I was able to snap it clean at the joint by hand with little pressure the next day.

Many WO products are made with multiple purposes, which makes them jack of all trades and master of none. 16 is one of these. If this is a critical joint and you choose 16, make sure the pipe is well supported because IMO it's not the right stuff to use. I'm just sayin that the last thing you want is to accidentally bump the pipe and your joint will let loose, then you have a difficult repair to perform while the tank is full. Not to mention the fact that when the tank is full it will flex and put pressure on this joint.

still....never done exactly what you're doing.

So do you have a picture of what you're trying to do? Maybe I'm not quite understanding...
 
H20ENG said:
Hotpuppy,
I've welded pvc to acrylic before with 16, years ago. It was ugly and I knew better, but it held. BUT I used the flat half of a union with a nice large gluing area, not just the end of a coupling.
FWIW
Click to expand...

Hmm, I was thinking that by upsizing the coupling from a 1 inch to a 2 inch I would get more glue surface. I'm having a hard time imagining a 1/2" thick joint of acrylic to PVC as being fragile.... dunno I'm gonna torture a test panel here in a minute. :)
 
Floyd R Turbo said:
40 does 'bite' into acrylic (dissolves it), it's not just a glue.epoxy. As far as it biting into PVC I don't know from experience. But as for bod quality, this has mostly to do with the operator (i.e. a joint is only as good as you prepare it to be).

Perhaps my attempt at welding PVC to acrylic with 16 was not done correctly. I only tried it once (and did not rough up the PVC surface) but I was able to snap it clean at the joint by hand with little pressure the next day.

still....never done exactly what you're doing.

So do you have a picture of what you're trying to do? Maybe I'm not quite understanding...
Click to expand...

Yes, abrading the surface is critical.... PVC comes with a smooth finish that is almost non-stick.

Here are some pictures of my test panel:

a 2 inch PVC coupling in a 1/2 inch sheet
DSCN0062.JPG

a 1 inch PVC coupling in the same 1/2 inch sheet
DSCN0063.JPG


Side view of the 1 inch. The 1 inch had a 2mm gap, so I was really impressed the wo16 actually filled the gap as it was larger than I thought was workable.
DSCN0066.JPG


Applicator syringe by West System (available at West Marine)
DSCN0066.JPG
 
I went out and put the panel in a vise, mounted to a bench.

I then proceeded to remove the 1 inch fitting. First I used a pair of pliers to grab it and applied as much forced as I was able to. I'm a normal sized American guy (5'11", 200#), I'm in reasonably decent shape..... To say the least, I could not simply rip the thing out. The 1 inch coupling visibly deflected.

I then took a pipe wrench and proceeded to beat the coupling out. It took over 7 blows before it began to move and finally popped out around 10 blows. This was a 18" pipe wrench.

Inspection of the failure shows it was adhesive failure, most likely due to excessive thickness as neither the PVC nor the Acrylic came off. The joint is also only about 14 hours old, so it has not developed full strength.

Keep in mind, my objective was to perform destructive testing on the 1 inch coupling.... I'm reasonably confident in saying that my tank or sump should *never* experience hammering. I'm pretty sure that the SCH80 Bulkhead nut would have broken under the same load.
DSCN0068.JPG

DSCN0069.JPG


The hole:
DSCN0070.JPG


The test jig with a 10" piece of 2" PVC Sch 40 inserted (not glued)
DSCN0071.JPG


Non-scientific 27 pound side load test - I took a vacuum pump and inserted the handle in the end of the pipe and let it hang there..... that's 27 pounds of side load. I weighed the pump on a shipping scale after the test. Now arguably the push fit deflected, but after that the load is still being born by the joint. I think 27 pounds is more than my pipes are going to experience in the event of an accidental grab.
DSCN0072.JPG


The 2 inch coupling has far more surface area.

In summary here is what I think I've figured out:
- In acrylic of sufficient thickness you can solvent weld PVC fittings of adequate diameter. Diameter yields joint surface area.
- WO16 will deliver water tight, but cosmetically inferior joints that have adequate strength.
- The joints will take some impacts, and moderate side loading - both momentary without failure.
- Due to the permanent nature of the bond it's important to keep in mind that it may be impossible to undo plumbing if it's solvent welded to a fitting.
- It's important to have a close fit to minimize the thickness of the adhesive as the adhesive itself is not as tough as PVC or Acrylic.
- It's important to mechanically secure plumbing to minimize the opportunity for undesirable movement which might otherwise stress plumbing fittings.
 
Like Floyd, I would sress to you not use this method for creating a bulkhead. I used that fitting to fill a kalk reactor. The high surface area I mentioned is about the same as a cheap bulkhead. The biggest issue is supporting your plumbing. One bump of an unsupported pipe and its all over.
I've solved space issues in overflows by drilling the back wall to add fittings. Yes it adds tank depth but I needed that safety overflow. You could always add acrylic to exted the OF box then drill a new bottom hole.
 
Hotpuppy said:
Anyhow.... I think for bond clarity, 40 is the way to go. for bond quality, 16 is the way to go. Here's my thinking. 16 contains solvents that dissolve both. 40 isn't solvent based. It's a monomer and a catalyst. You mix it and it thermosets into acrylic. That's why it works good to fill holes and bond large sheets.
Click to expand...
Actually, this isn't true. WO 16 is primarily methylene chloride and monomer. Methylene chloride does *not* dissolve PVC appreciably at all. Try it sometime. Therefore there is no solvent bond, period. For equivalent joint strength you could use PVC pipe cement if you wish, doesn't mean it's the best option.

I don't care what IPS says, there is virtually *nothing* that 16 does that 40 won't do better.

Since you had implied you were looking for credentials: My opinion is based on several decades of building tanks for public aquariums, there are a good number people here who know me personally and can attest to this :)

As for bonding PVC to acrylic, yes - done it several times. There are several methods of doing this as well. MEK is the *only* solvent that attacks both PVC and acrylic appreciably.

James
 
Just a note on your "side load test". I believe what you are testing is torque if not I think the principle will still apply. You have applies 27 lbs at 10 inches (just a guess from the picture). If you have a four foot drop to the sump then about a 5.6 lbs force on the end of the pipe would create the same "side load". Just remember as the pipe gets longer the forces on the joints increase.
 
Acrylics said:
Actually, this isn't true. WO 16 is primarily methylene chloride and monomer. Methylene chloride does *not* dissolve PVC appreciably at all. Try it sometime. Therefore there is no solvent bond, period. For equivalent joint strength you could use PVC pipe cement if you wish, doesn't mean it's the best option.

I don't care what IPS says, there is virtually *nothing* that 16 does that 40 won't do better.

Since you had implied you were looking for credentials: My opinion is based on several decades of building tanks for public aquariums, there are a good number people here who know me personally and can attest to this :)

As for bonding PVC to acrylic, yes - done it several times. There are several methods of doing this as well. MEK is the *only* solvent that attacks both PVC and acrylic appreciably.

James
Click to expand...

James,
I think your credentials are well established.....

What was the outcome of PVC to Acrylic joints over time?

I happen to have some MEK from a fiberglass project.... Is it a typical solvent weld? It seems a bit thin, what can be done to thicken it, acrylic shavings?

Thanks
 
TheFishMan65 said:
Just a note on your "side load test". I believe what you are testing is torque if not I think the principle will still apply. You have applies 27 lbs at 10 inches (just a guess from the picture). If you have a four foot drop to the sump then about a 5.6 lbs force on the end of the pipe would create the same "side load". Just remember as the pipe gets longer the forces on the joints increase.
Click to expand...

Correct, it's a torque test and yes length acts as a multiplier, although PVC pipe will absorb some of it as it's somewhat flexible in smaller diameters like 1 inch.

In this particular application the pipe will be physically secured to the stand. The large diameter pipes will come down to a physical support (regardless of tank penetration method) and then exit the floor and sub-floor where they are glued with construction polyurethane as a moisture barrier and insect barrier. They are then secured to the underside of the floor joists on their way to the fish area.

The idea here was to see if the joint was brittle or otherwise fragile.
 
Within a reasonable context, it would take a fairly long pipe to deflect any significant torque away from the joint. You may be well served with a small section of SpaFlex to allow for expansion and contraction, and flexibility.
 
BeanAnimal said:
Within a reasonable context, it would take a fairly long pipe to deflect any significant torque away from the joint. You may be well served with a small section of SpaFlex to allow for expansion and contraction, and flexibility.
Click to expand...

SpaFlex is one option, although I think flex-hose and nipples would actually be a better solution. Spa-Flex PVC Solvent joints don't have good long term durability. Spa-Flex, like all PVC tends to become more brittle with age.... IME.

I had my buddy who does commercial plumbing and pools help me weld the top this morning. He was curious how the acrylic process worked.

We discussed bulkheads vs solvent and the outtake was:

-bulkheads are good in equipment where you need to remove the pipe to gain access, such as sticking your hand inside a filter.
-bulkheads are good when joining non weldable material such as glass and plastic.
-bulkheads in restricted access locations are a significant risk. In my installation it's unlikely that I will be able to get a wrench to the bottom of the tank if I need to rework a bulkhead fitting.
-bulkheads are a good repair or installation option when you do not have time to allow a proper solvent weld to come up to strength.

I showed him the test piece and we talked about it. He thought it looked like a good joint from a plumbing perspective. I asked him if he was installing this tank in a demanding customer's house which route he would go.... his answer without hesitation was solvent welded.

Now, the point of this being posted is not to antogonize, or argue about what everyone else does.... I know what everyone else does..... I'm interested in a durable long term solution that reduces the possibility for difficult to service locations. The location of the return plumbing in particular is going to be very hard to service if there is a leak at the tank penetrations. Even if I cut an oversize hole to allow access it's going to be a major PITA to get in there between the frame members.

There are only a couple of reasons that would make me think a solvent welded joint is inferior to a mechanical seal (bulkhead).
- The joint exhibits stress cracking which leads to integrity failure within a period of time likely to be shorter than the service life of the tank in question.
- The joint is likely to endure stress failure due to something like children swinging from the pipes in the basement.
- Difficulty in fabricating the hole to the proper tolerance


The reasons a mechanical seal would be inferior:
- Installation into a difficult to reach / maintain area where preventative maintenance, checks, or repairs would be tedious.
- Installation requires space not available.


I put a call in to Cyro's Technical Support and was told it will work fine. Discussed all of the possible concerns and they concur with my analysis. They also recommended WO16 over WO40 saying that 16 will bite into both materials.

Maximum stated dimensional change of Acrylite GP is 1% after about 30 days due to water absorption. They believe this is well within the tolerance of PVC to simply expand with the acrylic.

I explicitly asked about stress cracks and was told that there shouldn't be any in the Acrylite. I asked if they had other customers doing this and was told yes, it's fairly common.

Plexiglas De Mexico (Chemcast GP) is identical to Acrylite GP per their website.

Finally - I look at it like this - If I'm wrong I'll have to drill a hole and install a bulkhead. If I'm right, it will save about $100 and be one less spot that can leak on my tank. (8 of them actually). The movement risks will be mitigated by securing the pipes adequately, as they should be anyhow.

Barring new information in the next day, I plan to solvent weld fittings in after I complete the tank water test. I'll share my experience in case someone else can benefit from it.
 
I guess the space issue is really the driving reason. If there's no space to put a bulkhead and then a 90, you have to figure something else out.

One point to comment on is that you should never take a wrench to a bulkhead nut. Overtightening the bulkhead can lead to cracking the tank. The gasket should be coated with silicone like this

http://www.lowes.com/pd_817-1409-GR2V-D_?PL=1&productId=3350380

and hand-tightened. Just another tidbit of info. You find all kinds of stuff on this site when searching for something else :)
 
Floyd R Turbo said:
I guess the space issue is really the driving reason. If there's no space to put a bulkhead and then a 90, you have to figure something else out.

One point to comment on is that you should never take a wrench to a bulkhead nut. Overtightening the bulkhead can lead to cracking the tank. The gasket should be coated with silicone like this

http://www.lowes.com/pd_817-1409-GR2V-D_?PL=1&productId=3350380

and hand-tightened. Just another tidbit of info. You find all kinds of stuff on this site when searching for something else :)
Click to expand...

I respectfully disagree on both counts.

first, silicone on top of a gasket forms a double gasket... this is not a best practice.

Second - a wrench can be used to snug the bulkhead nut to provide the proper pressure on the gasket. I have about 10 bulkheads installed this way and have yet to crack anything..... not saying it won't happen... Glass is unpredictable and once stress is induced it will do what it wants. However, I have bulkheads of a variety of sizes in several tanks of different sizes. Once I realized how easy it was to drill glass I put holes where I need them. I try to just compress the gasket and a wrench gives me more control..... so if you can do it by hand that's great. My hands hurt if I do too much strenuous work with them, so I use tools whenever appropriate. :)

I did find what I think is a show stopper.....
To properly seal these requires flipping the tank which would be difficult at best.

I found that when I drilled a tighter fitting hole that is snug, I need to use a needle to inject the WO16. It results in a better joint... but I have to flip the piece over and finish injecting glue while it's workable. That is fine when I'm putting together a overflow. It's unworkable for a large tank.

So, my overflow will have PVC fittings solvent welded in, and the tank will use bulkheads. Just means the bulkheads have to be put in before the tank is put in position and a leak will be a major ordeal - PITA.

I probably could have welded them in place before assembly, but it creates new issues of it's own.

This would also be a great reason to use WO40 as it will fill a gap.... although I'm not sure if it will melt the PVC based on just what it is.... a thermosetting monomer with a catalyst to cause it to polymerize/cure. I suppose if you roughed up the PVC enough you might get a mechanical bond... but that's not as good as a chemical bond. Epoxy might be another way to do it, but most epoxies are brittle IME.
 
Last edited:
Hotpuppy said:
SpaFlex is one option, although I think flex-hose and nipples would actually be a better solution. Spa-Flex PVC Solvent joints don't have good long term durability. Spa-Flex, like all PVC tends to become more brittle with age.... IME.
Click to expand...
You are doing it again :D (formulating assumptions and applying them as fact to support the answer you want to hear).

Properly intstalled flex pvc is not going to become brittle and fail in any reasonable environment and will be far less restrictive than a king nipple and hose. The irony is that your makeshift pvc to acrylic joint is in more danger of failing than a properly welded flex to hard pvc joint.

It would appear that your logic and assumption often find themselves in conflict with each other...

Good luck with your build :)
 
Floyd R Turbo said:
One point to comment on is that you should never take a wrench to a bulkhead nut. Overtightening the bulkhead can lead to cracking the tank. The gasket should be coated with silicone like this

http://www.lowes.com/pd_817-1409-GR2V-D_?PL=1&productId=3350380

and hand-tightened. Just another tidbit of info. You find all kinds of stuff on this site when searching for something else :)
Click to expand...

Hand tight plus a 1/4 to 1/2 turn usually means using a bulkhead wrench :)

As for the silicone grease... I properly installed bulkhead does not need silicone grease or sealant as the pressure of the flange against the gasket (exerted by the nut) is what provides the sealing force. The silicone grease only helps to allow the gasket to squish out of place under the pressure of the flange :)
 
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