How Much Teflon Tape - Slight Leak

[Tidybuoy]

Finished all my plumbing for my Tankless Water Heater. All joints were copper soldered until I get to the water filter, which is plastic. Once the water was turned on, I am getting a single drop leak about once an hour on both sides of the water filter/descaler. I thought I used plenty of teflon tape as I wrapped the threads about 3 times. What is the norm for this type of sealing.

On a separate note, I made the mistake of not putting in a union for the connection to the water filter. Guess what I'm doing tonight?

The leak is right where the copper threads into the black plastic filter:

[asphaltgambler]

Never use tape, it bunches up and folds when you tighten. Paste only...…….

[sammyg2]

The manufacturers of PTFE tape (teflon) say 1-1.2 wraps on new threads, 2-1/2 wraps on old threads.

But at least one of them I know of forbids using teflon tape on the hydraulic systems used on the machines that make the tape.
The problem is, if the connection is ever taken apart and re-assembled there's a good chance small pieces of the tape can end up in the hydraulic system and clog a valve or orifice.


Assuming it's wrapped in the correct direction, 2 to 2-1/2 wraps should do the trick as long as the threads aren't buggered all to heck.
I can't tell from the picture but if that filter housing is plastic, over-tightening it could cause leaks.
I would recommend using a teflon paste-type pipe dope instead of tape.
But the best (low temperature) pipe dope I've ever used is green key-tite.

[sammyg2]

The stuff I've used and had great results from looked like this:





But it looks like they've changed the packaging to this:

[cabmandone]

Originally Posted by asphaltgambler

Never use tape, it bunches up and folds when you tighten. Paste only...…….

I disagree. Use tape but also use PTFE pipe thread sealant too. A plumber taught me that.

[pmax]

Tried it before on PVC, teflon doesn't work. Makes sense to me since PVC isn't a hard surface where the tape can "bite" into and seal.

https://www.bing.com/search?form=MOZTSB&pc=MOZI&q=teflon+tape+on+plastic

[Bill Douglas]

Two and a half turns. I think that is what's causing the problem.

In the brass threads; rough them up with a large pair of pliers so the thread doesn't slip. My plumber friend says he does 13 turns. I check the tightness. If it's loose I do 14, if it's tight I do 12 turns.

Some joints I use hemp. I roll/stretch it out to be like fine string. Rub some copper grease (non-seize grease is good). Then wind that around. The good thing about hemp is it swells up a bit creating a water tight seal.

I'm thinking you guys tape may be thicker stuff than what we use. But the secret is to rough up the threads so it doesn't just spin around with nothing remaining on the threads.

[sammyg2]

https://en.wikipedia.org/wiki/Thread_seal_tape

https://plumbuniversity.com/teflon-tape/

[908/930]

On threads larger than 1/4 npt you should use the thicker tape, usually pink in colour, that thin tape will take about 15 wraps.

[Tidybuoy]

Well goofing off here at work, I looked up the owners manual for the filter and it states not to use pipe dope and only use teflon tape. It states to use no more than 7 wraps.

Reading thru this thread, I probably over tightened because I threaded the fitting all the way till it wouldn't go any further (you can see that in the photo). Tonight I will put in some unions so that I am able to dissemble - looking a the photo, you will see there is no way to unthread as is without removing the wall (my bad). I will look for the thicker tape and re-do. I know that I have, at home the heavy duty dark grey tape at home.

Regardless, I'm on the home stretch and was able to take a hot shower this morning - using buckets of water on the driveway was not fun over the weekend. Crawling under the house about 50+ times for re-plumbing the gas lines and water was not fun either. I was very surprised how quiet the tankless is - it barely makes a sound.

[Brian 162]

I used to tape the fitting really tight no more than 2 turns. I would then put pipe dope over the tape.
I never had a leak. It worked for me from 1/2 inch up to 3 inch fittings.
If you tightened the fitting all the way check the filter housing, make sure there's no crack in the filter housing.

[look 171]

Give it another 1/4 turn. It should seal it up well without cracking the plastic. We use both at the same time, have it on my "Heater Treater"

[rfuerst911sc]

I really don't have any expertise in plumbing but I do it because I can . In the past year regardless of what type of threaded fitting ( copper/metal/plastic ) I wrap 3-4 turns AND add pipe dope . Is that recommended ? Don't know . Does it work ? All I can say is every threaded joint I have done this on has not leaked . Not one drop !

My water heater install with CPVC no leaks . An airline for a boost gauge for my diesel pickup no leaks . Just two examples of success that I have recently had .

[NY65912]

No tape on plastic

[cabmandone]

Wrap a paper towel around each one and unwrap it in about 6 months. Leak will be gone.

[rfuerst911sc]

Originally Posted by NY65912

No tape on plastic

This old house article in step 1 states to use tape on plastic fittings .

https://www.google.com/amp/s/www.thisoldhouse.com/platform/amp/plumbing/21015973/when-to-use-sealants-on-threaded-plumbing-connections

[pmax]

Originally Posted by rfuerst911sc

This old house article in step 1 states to use tape on plastic fittings .

https://www.google.com/amp/s/www.thisoldhouse.com/platform/amp/plumbing/21015973/when-to-use-sealants-on-threaded-plumbing-connections

From the folks who make them ...
whose recommendation matches up with my limited knowledge here.

https://www.bing.com/search?form=MOZSPG&pc=MOZI&q=threaded+PVC+joint
https://www.lascofittings.com/threads

The "Do's and Don'ts" of Assembling Threaded Plastic Fittings

Today, there are millions of miles of plastic piping with threaded fittings, providing reliable, leak-free service. However, a tiny percentage of those threaded plastic fittings may leak or break. The reason for this is improper assembly of threaded joints.

Here are some of the Do's and Don'ts of PVC joint assembly:

Don't over-tighten joints by giving them "one more turn to be sure."Do finger tighten plus one or two turns - No More.
Don't wrap Teflon tape or Teflon paste or pipe dope to add bulk to or to lubricate the joint. Do use a sealant for threaded joints.
Don't use "stronger" Schedule 80 threaded fittings on the assumption that they may solve the problem of splitting through over-tightening.
Do use only Schedule 40 threaded fittings with Schedule 40 pipe and fittings.
Don't over-tighten.
Do finger tighten plus one or two turns.

On threaded male PVC fittings each successive thread is slightly larger in diameter than the one before it. Female threads get successively smaller. This is called taper and the amount of taper is specified (1¾ degrees) in the American National Standard B2.1. All pipe manufacturers voluntarily follow these standards to assure their customers they are receiving quality materials.

Because the threads are tapered, additional turns cause the female part to stretch or undergo "strain." This will split the female fitting just as a wedge, driven by a sledgehammer, will split a tree stump.

The amount of strain increases as the size of the pipe decreases. Therefore it is easier to split smaller diameter threaded joints than larger ones. It is also easier to over-torque smaller diameter fittings because their resistance to torque is less. Table 1 gives Strain and Tensile Stress levels according to pipe diameter.

... lots of good plumbing tech stuff ... will read later !

[rfuerst911sc]

Looks like the experts disagree imagine that 😁 . I will continue to do what works for me . Good discussion .

[red-beard]

I use the white tape (5 turns) on water pipes and the yellow gas tape (3 turns) on gas pipe (black iron), etc. I usually run the threads first with a die to make sure they are clean.

Make sure you wrap it the correct direction, so that the tail is in the direction of the direction of rotation, so it doesn't bunch up. Also, cut the tape with a knife or scissors, instead of tearing it.

[plumb4u2]

Ok so I’m not going to comment on all the “expert” advice!

You never use pipe dope on plastic threads TAPE ONLY! Dope will weaken the plastic over time and provide you with a happy flood!
I have a couple pieces of advice on what I can see in your photo (not criticizing your install just trying to help!). Your gas valve and union need to be swapped, gas valve comes first so you can shut off gas then crack union to service the unit.
Please run relief discharge to 6” above the floor and do not use that PVC, it must be cpvc or copper!! Pvc is only rated for 73 degrees if that relief valve blows the pvc will melt and potentially hurt someone