Do plastic and brass threaded fittings good with each other

[Asker123]

Hi there,
Pictures below
My new softener system has this bypass valve and a fitting that which has 1" MNPT at its end in black color. It is part of a Fleck 5810 valve system so I assume its a very good quality plastic/fiberglass ( sorry I do not understand materials in detail)

I bought a Brass Pex fitting it is 1" FNPT and 1" Push to connect on the other end. Its from Sharkbite. I am seeing two issues.
1) The threads do not go all the way in . There are total 6 threads on the black valve side Male thread fittings but only 3 go in when I am done hand tightening the Brass fitting.
2) The brass fitting seems very heavy . Will that be an issue that it will generate stress on that joint.

The softener company sent me a fitting made with similar black plastic kind material. Looks very high quality and super light and goes all the way in ( all threads of male and female side engaged) but it is 1"FNPT to 3/4 inch Push-To Connect on the other end. I dont want to reduce the size from 1 inch to 3/4 inch.

What do you guys think?

 

[Gsmith22]

those are NPT threads - they taper and are not intended to be screwed all the way in. Its not like a bolt and nut where the nut goes all the way down and seats against the materials the bolt and nut are holding together. Because of the thread taper, the threads essentially interfere with each other as you tighten. there are many posts about this so do some searches but in essence, you tighten by hand and then do a turn or two more with a wrench. It isn't uncommon to have two to three treads remaining exposed on the male side of the threaded part.

Typically you want to use some combination of tape and pipe dope on the threads to seal and lubricate the threads.

When using these types of fittings and mixing plastic and a metal, you always want the female side (the receiving side) to be metal and the male side (exposed threads on outside of part) to be the plastic side. If the plastic is the female side it will typically split as the joint is tightened regardless of how good the plastic material is.

 

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[Asker123]

Thank you so much for clarification gsmith22.
Any consideration of the weight of this Brass fitting? It is very heavy compared to the other plastic fitting the softener company sent. Its just that they sent it wrong size ( 1 inch to 3/4 inch) . I am unable to find a 1 inch FNPT to 1 inch Push to Connect in this Black plastic kind of material locally at home depot or even local plumbing stores so have to depend on this Sharkbite. Do you/anyone else see any concern?

My other option is to find a 1 inch FNPT to a 1 inch Pex fitting. May be that fitting even in brass will weigh much less than this sharbite fitting. But sharkbite is Push to connect.

Are flexi connectors such as below offer remarkable advantage over the sharkbite brass fitting I showed above.

Easy Install Kit 1" Female x 1" Push-To-Connect

Make water system installation a breeze with the Aquatell Easy Installation Kit. Features 2 x Falcon connectors (1" Female) with push-to-connect ends.

www.aquatell.ca

 

[Fitter30]

Sharkbite makes 1" fittings hardware store or a box store should either have them or order them. 1" x 1" either fpt (female)

 

[Tuttles Revenge]

Be very careful threading plastic into brass however, any cross threading will destroy the male plastic threads. Otherwise as noted above, both male and female fittings need to be tapered.

 

[Asker123]

Sharkbite makes 1" fittings hardware store or a box store should either have them or order them. 1" x 1" either fpt (female)

The Brass one that I have put in pic is indeed Sharkbite. Do you want to say Sharkbite also makes those in Black plastic/PVC/whaetever that light material is as well?

 

[Mr tee]

If you keep Teflon/dope a couple threads back from the end you are less apt to cross thread and it will not effect the seal.

 

[Gsmith22]

The Brass one that I have put in pic is indeed Sharkbite. Do you want to say Sharkbite also makes those in Black plastic/PVC/whaetever that light material is as well?

the black plastic is probably an engineered polymer and not readily available from a big box store or even a plumbing supply. the water softener company probably has various parts made from it for their equipment. I wouldn't worry about the weight of a brass fitting attached to it. engineered polymers are quite strong.

Again, you don't want the female brass part to be plastic because it will have to resist forces in a tension ring as the threaded plastic part is screwed into it. Plastic and tension don't like each other. You want the female threaded part to be a metal. You aren't going to generally find the female part in plastic anyway for this reason (exceptions might be pvc or cpvc but you don't want those here anyway)

 

[Reach4]

When screwing into a fitting, I like to turn CCW a few time, noting where the threads fall in. Then just past the fall-in I would start going CW.

Make sure the dope is ok for your plastic. For example, https://www.oatey.com/products/hercules-megaloc--1330684393 says "plastic" without having to list which plastic.

Dope and tape both are less likely to leak.

Examine the threads on the plastic. If they have mold marks, there is more likely to be a leak I think.

 

[Asker123]

the black plastic is probably an engineered polymer and not readily available from a big box store or even a plumbing supply. the water softener company probably has various parts made from it for their equipment. I wouldn't worry about the weight of a brass fitting attached to it. engineered polymers are quite strong.

Again, you don't want the female brass part to be plastic because it will have to resist forces in a tension ring as the threaded plastic part is screwed into it. Plastic and tension don't like each other. You want the female threaded part to be a metal. You aren't going to generally find the female part in plastic anyway for this reason (exceptions might be pvc or cpvc but you don't want those here anyway)

OK Thanks gsmith22.
The link below, that I was supposed to get does have similar looking Black engineering Polymer Female Thread fitting. I was stupid enough to order 2 of those that have 1 Inch female to 3/4 inch PTC on the other side. Indeed I am going to use one for the output of the softener. Then when I visited this site, I was advised to go 1 inch from my pressure tank to the softener . Unfortunately such fitting as shown below is not in Big box stores and it will take me 2 weeks and almost 100 Canadian dollars to get a pair that has 1 inch Push to Connect on other side.
This is my home for life and I want to get it right the first time so may be I can wait but question is whether its worth all this effort?

Easy Install Kit 1" Female x 1" Push-To-Connect

Make water system installation a breeze with the Aquatell Easy Installation Kit. Features 2 x Falcon connectors (1" Female) with push-to-connect ends.

www.aquatell.ca

 

[Gsmith22]

OK Thanks gsmith22.
The link below, that I was supposed to get does have similar looking Black engineering Polymer Female Thread fitting. I was stupid enough to order 2 of those that have 1 Inch female to 3/4 inch PTC on the other side. Indeed I am going to use one for the output of the softener. Then when I visited this site, I was advised to go 1 inch from my pressure tank to the softener . Unfortunately such fitting as shown below is not in Big box stores and it will take me 2 weeks and almost 100 Canadian dollars to get a pair that has 1 inch Push to Connect on other side.
This is my home for life and I want to get it right the first time so may be I can wait but question is whether its worth all this effort?

Easy Install Kit 1" Female x 1" Push-To-Connect

Make water system installation a breeze with the Aquatell Easy Installation Kit. Features 2 x Falcon connectors (1" Female) with push-to-connect ends.

www.aquatell.ca

the push to connect obviously makes it very easy to connect that flex hose to the houses plumbing. In general flex hoses are recommended between equipment (like a softener) and the house's plumbing. Do you need them? No but it probably is better with than without. 1" is probably not a common stocked item at big box stores.

a local plumbing supply or www.supplyhouse.com might be better options anyway than big box stores. I have pretty much stopped buying anything plumbing related from big box as the quality is terrible with lowest cost outsourced items now standard stocked.