How to connect IPS to NPT.

[EthylOH]

Hi all,

I have a tub faucet that I need to connect.

http://www.kingstonbrass.com/v/images/tech/measurement/CC1T8.pdf

This will be an on-the-wall installation. I have 3/4" NPT drop elbows mounted in between the studs.

When I tried to thread the faucet, I couldn't get the threads to completely seat. Then I realized that the faucet has IPS threads with no taper, which is why it keeps binding in the drop elbow.

How can I connect this? Is there an IPS/NPT adapter?

 

[EthylOH]

I was thinking....

Any reason I can't just buy a 3/4" NPT die and cut the threads?

 

[Sponsor]

 

[EthylOH]

Or am I better off buying a 3/4" tap and turning the drop elbow into a non-tapered IPS fitting?

That way, if I screw something up, it's only a $5 part instead of an integral component from a $300 faucet.

 

[Jadnashua]

I have a similar product (different company) that mounts to the wall. It came with the required adapters. You sure there aren't any in the box or shown in the parts list?

Can you get to the fitting in the wall? You might just replace it with a hose type adapter. That type of fitting relies on a gasket to seal by compressing it when you tighten it down as opposed to a tapered fitting which requires tape or pipe dope to create the seal.

 

[EthylOH]

I have a similar product (different company) that mounts to the wall. It came with the required adapters. You sure there aren't any in the box or shown in the parts list?

Can you get to the fitting in the wall? You might just replace it with a hose type adapter. That type of fitting relies on a gasket to seal by compressing it when you tighten it down as opposed to a tapered fitting which requires tape or pipe dope to create the seal.

Jim,

I checked and then checked again - no adapters...

I still have full access to everything, so I can use any setup I need.

However, isn't it not the best idea to bury flexible supply lines in a wall? Don't they have a limited life time, sort of like washing machine hookups?

Any reason not to either tap the drop elbow to NPS, or taper the threads to NPT? Which would be the better option?

Here's a pic of the setup:

 

[CountryBumkin]

You want NPT (National Pipe Taper) to NPS (National Pipe Straight) adapter. IPS (Iron Pipe Straight) and NPS are the same thing.

See http://www.amazon.com/Nelson-Industrial-Fitting-Female-50572/dp/B0015AT0BE
Or http://www.amazon.com/dp/B0015ASX12..._m=ATVPDKIKX0DER&pf_rd_r=0GZ5566GXSBV4KNG74B1

 

[Terry]

Normally that faucet uses risers like these.

 

[EthylOH]

View attachment 34554 You want NPT (National Pipe Taper) to NPS (National Pipe Straight) adapter. IPS (Iron Pipe Straight) and NPS are the same thing.

See http://www.amazon.com/Nelson-Industrial-Fitting-Female-50572/dp/B0015AT0BE
Or http://www.amazon.com/dp/B0015ASX12..._m=ATVPDKIKX0DER&pf_rd_r=0GZ5566GXSBV4KNG74B1

I saw those yesterday. I may be wrong, but those are listed as garden hose threads, so they won't be compatible.

 

[EthylOH]

Normally that faucet uses risers like these.

Terry, you're correct.

But it is also sold as a wall-mount-faucet. The instructions even address mounting it in a wall. Of course, it says "connect supply lines" without any consideration given to the fact that most in wall plumbing will have NPT threads...

I'm just going to rethread either the elbow or the pipe.

I assume either this for the elbow:
http://www.amazon.com/High-Speed-Steel-Straight-Pipe/dp/B00268D0EC

Or this for the pipe:
http://www.homedepot.com/p/RIDGID-3-4-in-OOR-NPT-Die-Head-36895/100160469

Harbor Freight also has a Ridgid die set knock-off (which gets very mediocre reviews at best), but I'm afraid of the risk of ruining the threads on the faucet pipe.

 

[Jadnashua]

You don't want a hose in the wall, but a hose threaded fitting may just be what you need. The adapter that came with mine had a NPT on one end, and a straight thread on the other end that mated up with the valve assembly. One end required the use of a gasket to seal, the other end used pipe dope or tape which connected to the drop-ear el in the wall. I don't know if the thread pitch is the same...if it is, threading it (you'd probably need a bottoming tap if it's a female) should probably work. If the thread pitch isn't the same, you'd have a very weak connection and probably have trouble threading things together without cross-threading.

 

[EthylOH]

You don't want a hose in the wall, but a hose threaded fitting may just be what you need. The adapter that came with mine had a NPT on one end, and a straight thread on the other end that mated up with the valve assembly. One end required the use of a gasket to seal, the other end used pipe dope or tape which connected to the drop-ear el in the wall. I don't know if the thread pitch is the same...if it is, threading it (you'd probably need a bottoming tap if it's a female) should probably work. If the thread pitch isn't the same, you'd have a very weak connection and probably have trouble threading things together without cross-threading.

Thanks Jim,

I stopped by Lowes and they had a hose/NPT adapter. I actually brought the faucet pipe and drop elbow with me to test.

The NPT threads threaded into the drop elbow nicely, but the faucet pipe bound up about two threads into the hose side of the adapter.

I thought garden hose thread (GHT) was it's own class of fitting with 11.5 TPI instead of the 14 TPI for NPS?



Also, when you mention the tap pitch as being different, are you referring to loose manufacturing tolerances?

This is the tap I plan on getting:

http://www.amazon.com/High-Speed-Steel-Straight-Pipe/dp/B00268D0EC

It says it's for NPS threads, so wouldn't that mean it should work? Also, the description even says "NOT tapered."


In the question section on the Amazon listing, it looks like another person had the exact same problem as me.
Here's the quote from Amazon:

"Question:

Can I use this to convert female npt to npt coupling into npt to nps coupling by following threads into coupling for 6 or 7 turns?

Answer:

Not quite sure about your question. Assume your looking to use this tap to convert taper threads in a female fitting to straight. Yes this will work but you may need to tap drill for the straight tap if the turning gets tough. Remember though screwing a male taper pipe into this straight thread will produce a crappy seal if that what's what you need. see less
By Duane B. on March 9, 2016" ​

 

[Jadnashua]

The threads might just be metric on the valve you bought...that would complicate things quite a bit. NPT is a tapered thread. If they say it is a straight thread, and you should be able to verify that, then, you need to find out what the actual pitch and diameter is before going much further.

 

[EthylOH]

The threads might just be metric on the valve you bought...that would complicate things quite a bit. NPT is a tapered thread. If they say it is a straight thread, and you should be able to verify that, then, you need to find out what the actual pitch and diameter is before going much further.

The manual lists the fittings as "standard US plumbing connections," and the parts diagram shows the threads as 3/4" IPS.

 

[EthylOH]

PROBLEM SOLVED! (I think)

I bought a swivel fitting at Lowes. The threads line up and compress the seal perfectly. I just need a washer or two to secure it from the back.

I'm still putting in an access panel right behind the fittings though.

Any reason not to do it this way?

 

[Jadnashua]

Sounds like a plan. Consider, though, a major reason to use PEX is that it bends, eliminating the need for most connector fittings. Each one adds its own little restriction. It doesn't have to look neat to work.

Is there a big nut and washer that holds the valve to the wall?

 

[EthylOH]

Sounds like a plan. Consider, though, a major reason to use PEX is that it bends, eliminating the need for most connector fittings. Each one adds its own little restriction. It doesn't have to look neat to work.

Is there a big nut and washer that holds the valve to the wall?

Agreed on PEX's ability to eliminate fittings. Unfortunately, this is a 2x3 interior wall, so there isn't enough room to make a 90 degree bend with 3/4" PEX, so I have to use the fitting.


The washer/nut are where things might get a little hairy...

There is a black plastic threaded washer that comes with it to secure it on the inside of the wall (it's visible in the pic in post #5). However, since most finished tile walls are right around 1" thick, there isn't enough room for the lock washer and the threaded supply fitting on the end. The manufacturer will sell you two extension pieces for the low low price of only $50, but then the pipe becomes too long for the 2x3 wall depth.

Luckily, my finished wall depth will leave just enough room to fit a 3/4" brass washer in between the fitting and the wall, with the fitting doing double duty as the tightening nut as well. It it's too tight, I'll have to remove a tiny bit of Durock with a spade bit, and if it's too loose, I'll have to add a shim or two. Tight tolerances, I know, but the access panel will make this possible.


This is sold as a either a tub mount or a wall mount, but realistically, it should only be sold as a tub mount. There are too many design idiosyncrasies with it to be used as a wall mount.

 

[Mark Pavinich]

There is an adapter out there for this --- the adapter is NPS to IPS -- you can get whatever size you need. You will not find it at the local
Note, you can get it in chrome as well.

https://www.faucet.com/elements-of-...-and-3-4-ips-connections-from-the-hot/f149131

If you use GHT or other pipe sizes, you will only make the leak occur later. Do it right and have peace of mind by getting the actually fittings to do what they need to do. The IPS side of the adapter comes with a gasket / washer to form the seal as expected and designed. Remember IPS needs a gasket not tons of tape and pipe dope trying to make / force the seal. NPT, you can tape and/or dope.

Also, don't over pay! You get a pair for approximately $14 plus shipping

 

[Tbucket]

Found this thread searching since I'm currently in the same boat using the same faucet. My faucet is going through the tile wall and needs to connect to the copper lines. I think I'm going to use the adaptors Mark suggested and add a 90* elbow on the end to drop down to the copper lines, but wanted to throw another idea out there and see what you think. Would corrugated copper flex lines for a water heater work? Or SS corrugated flex lines for a water softener? They give good flow through a water heater and screw/seal into the tapered NPT fittings (even though I believe there straight thread?). I'm lucky in that the other side of the wall with the lines is built in drawers so I could pull the drawers out and get to the flex lines if needed.