Building an RODI unit, seal fittings?

[MarcosTacos]

I bought a used rodi unit for really cheap and am going through it to refurbish it. I bought new filters and all the jazz.

I was wondering if I should use teflon tape or even teflon paste or nothing on the fittings or other parts of the unit?

 

[Reefering1]

Teflon tape!

 

[MarcosTacos]

I heard teflon tape was not suitable for plastic on plastic fittings

 

[Lebowski_]

Teflon tape!

Do not listen to this @MarcosTacos. Teflon is not good for plastic fittings.

"When PTFE tape is wrapped around plastic male threads, it packs the threads, increases the pipe diameter, prevents the pipe threads from meshing properly, and adds strain and tensile stress."

My spectrapure plastic threads were hand-tightened.

 

[Reefering1]

Do not listen to this @MarcosTacos. Teflon is not good for plastic fittings.

"When PTFE tape is wrapped around plastic male threads, it packs the threads, increases the pipe diameter, prevents the pipe threads from meshing properly, and adds strain and tensile stress."

My spectrapure plastic threads were hand-tightened.

Idk, it sure stopped the fittings on my rodi system from leaking. Of coarse there is a right and wrong way to do anything. What do your papers suggest you do if fittings are seeping/ leaking, keep tightening and hope you don't crack the housing?

 

[cilyjr]

There is a rubber gasket at the top of each housing. They can bought at a plumbing supply shop like Ferguson.

They will appear fine but will sometimes leak. You will not often be able to see the small cracks in these gaskets.

 

[MarcosTacos]

I do have orings in the top of the housings. I was more wondering about the ro tubing fittings you thread in the different ends of the filter heads.

 

[robotrash]

A picture of what you're looking to attach may clarify for folks : )

 

[cilyjr]

I do have orings in the top of the housings. I was more wondering about the ro tubing fittings you thread in the different ends of the filter heads.

Oooohhh. The threaded to push to connect fittings.
I usually do one thin wrap of TPFE tape or a PVC thread sealant of some sort.

The above posts are correct. If you wrap several wraps of TPFE tape around those you can potentially crack the female side of fitting.

 

[cilyjr]

I do have orings in the top of the housings. I was more wondering about the ro tubing fittings you thread in the different ends of the filter heads.

You mean these?

 

[mfinn]

I stopped using tape on plastic fittings years ago when I used too much and the fitting cracked in the middle of the night. ( 80 gallon water spill). I used tape for a couple decades and never had a problem, but all it takes it one time.
Now I use only pvc paste.

 

[SteveMM62Reef]

I’ve always used Teflon Tape on Tapered and non-Tapered Plastic Fittings to keep from Friction Welding them together. As a Tradesman, I had a guide, that told you how many wraps to make depending on the pipe size. Also I’d get the locking clips, to keep the push in connections from pulling apart. Use an open end wrench to push the Collar back to release the tubing. BTW, Silicone can disable your Skimmer.

 

[BeanAnimal]

Several partially correct answers here...

Teflon is suitable for both tapered and not tapered Plastic or Metallic fittings, but must be used with caution.

On a tapered fitting (NPT for example) the teflon tape adds diameter and lubricity, making it very easy to over-tighten the fitting. The can cause extra stress on the female fitting and in some case cause it to crack. Typically (Steve mentioned above) there is a lookup table for the number of wraps for given fitting size and thread tape thickness.

The problem is that most of the fitting that you as a hobbyist are exposed to are low tolerance injection molded garbage that have almost zero chance of sealing with the proper amount of tape and force.

On a non tapered fitting, the added diameter may help seal the fitting but "more turns" will not typically stop a leak even each turn does not add significantly more stress to the female fitting.

In low pressure applications PTFE paste alone or with a wrap of PTFE tape can help if the fittings are decent quality.

I prefer hardening or semi-hardening pipe dope or joint sealer but potable and reef-safe become an issue.

For a typical RODI housing and the threaded to push fittings, a wrap or two of PTFE tape will almost always be sufficient. The housing are huge and there is no chance of the male fitting cracking or deforming the housing and you can in effect wrap enough PTFE tape to force the small fitting to the housing in a watertight manner. A dab of PTFE paste may help but is usually not needed.

For larger PVC fittings - I suggest skipping the LASCO and other big box stuff and buying quality schedule 80 fittings from Hayward, Spears etc. You will have far better luck with a wrap or two of PTFE tape or PTFE paste due to the far tighter tolerances.

 

[MarcosTacos]

You mean these?

Exactly

 

[Buckeye Hydro]

Yes - use teflon tape on the fittings.

If you need new housing orings, you'll need to go back to the original manufacturer as housing orings are nonstandard and vary between brands.

 

[BeanAnimal]

If you need new housing orings, you'll need to go back to the original manufacturer as housing orings are nonstandard and vary between brands.

Understatement of the decade. I am not sure most resellers anymore even know what housing they have out there. I just replaced 4 housing because I wasted more time trying to find o-rings than it was worth.

My advice would be to order a pile of o-rings when you get housings, and make sure they match day one, as you will have nothing but headache a year or More down the road when you need to order one.