Plastic nipples to connect water filter?

[Garn]

The very common Pentek Big Blue water filter housings have 1" FPT inlets and outlets made of polypropylene, as do many similar filter housings. Many much taller filters and water conditioners have MNPT inlets and outlets that seem easiest to connect using flexible steel connectors with FIP ends, but connecting to the plastic FPT on the Pentek-type filters would seem to require a PP or PVC nipple, given that it's not a good idea to thread metal into plastic. Strangely, to me at least, neither of the big box retailers sells any kind of 1" plastic nipple that's approved for potable water. Amazon and some smaller retailers sell them, but they're very expensive for plastic, presumably because they're fairly hard to find. How is the connection usually made?

 

[Reach4]

I am unaware of a problem threading metal into plastic. There is often a warning about using female threaded connections, but with the big blue, it seems pretty beefy around the threads. For water wells, they often use female couplings to connect schedule 80 PVC pipe, but those are usually schedule 120 or 160.

I suggest using both plastic-safe pipe dope and PTFE tape.

https://rectorseal.com/fip-x-mip-water-connectors/ has MNPT on one end.

 

[Sponsor]

 

[Garn]

I am unaware of a problem threading metal into plastic. There is often a warning about using female threaded connections, but with the big blue, it seems pretty beefy around the threads. For water wells, they often use female couplings to connect schedule 80 PVC pipe, but those are usually schedule 120 or 160.

I suggest using both plastic-safe pipe dope and PTFE tape.

https://rectorseal.com/fip-x-mip-water-connectors/ has MNPT on one end.

Thank you for your reply and link, Reach4. Sources like https://www.irrigationtutorials.com/faq/connections.htm offer good explanations of why metal shouldn't be threaded into plastic, which is probably the warning you were referring to. You make a good point, though, about the plastic on the filter housing being much stronger than a typical PVC female end. The filter I'm installing calls for shutoffs on each side, and the plastic shutoffs are 1/3 the price of brass while also less beefy than the filter housing, so the least expensive solution, if it won't leak, would be plastic nipple to shutoff to plastic nipple to filter on each side. Home Depot sells "risers" that are essentially PVC nipples, but they're for outdoor, irrigation use only. Lowe's sells Schedule 80 PVC nipples that are for non-potable water only. Both are very inexpensive. Do you have any theory why they don't offer plastic nipples one could use for potable water? The approved plastic nipples available elsewhere are roughly the same price as stainless steel ones. Would the plastic ones have any disadvantages?

 

[Reach4]

Thank you for your reply and link, Reach4. Sources like https://www.irrigationtutorials.com/faq/connections.htm offer good explanations of why metal shouldn't be threaded into plastic, which is probably the warning you were referring to. You make a good point, though, about the plastic on the filter housing being much stronger than a typical PVC female end. The filter I'm installing calls for shutoffs on each side, and the plastic shutoffs are 1/3 the price of brass while also less beefy than the filter housing, so the least expensive solution, if it won't leak, would be plastic nipple to shutoff to plastic nipple to filter on each side. Home Depot sells "risers" that are essentially PVC nipples, but they're for outdoor, irrigation use only. Lowe's sells Schedule 80 PVC nipples that are for non-potable water only. Both are very inexpensive. Do you have any theory why they don't offer plastic nipples one could use for potable water? The approved plastic nipples available elsewhere are roughly the same price as stainless steel ones. Would the plastic ones have any disadvantages?

I have not paid attention to being approved for potable water for nipples. One thing I have noted is that the cheap plastic nipples have mold marks rather than the threads being cut.

What size nipples would you be looking for?

How do you hold up the filter?
Note that the housings are not tapped for hanging from the bracket
if you buy the housing separately. They expect you to use 5/16 x 1
inch lag bolts. I suggest stainless.

 

[Garn]

I have not paid attention to being approved for potable water for nipples. One thing I have noted is that the cheap plastic nipples have mold marks rather than the threads being cut.

What size nipples would you be looking for?

How do you hold up the filter?
Note that the housings are not tapped for hanging from the bracket
if you buy the housing separately. They expect you to use 5/16 x 1
inch lag bolts. I suggest stainless.

Thank you. I'm looking for 1". I will have the filter sit on its bottom, not be held up by its connections. Do you still suggest stainless, and if so, is that because stainless would be cut, not cast?

 

[Reach4]

Stainless or brass or schedule 80 CPVC.

https://www.supplyhouse.com/Brass-Nipples-163000

https://www.supplyhouse.com/PVC-Sch-80-Nipples-21370000

https://www.supplyhouse.com/Stainless-Steel-Nipples-20480000

 

[Garn]

Stainless or brass or schedule 80 CPVC.

https://www.supplyhouse.com/Brass-Nipples-163000

https://www.supplyhouse.com/PVC-Sch-80-Nipples-21370000

https://www.supplyhouse.com/Stainless-Steel-Nipples-20480000

Thank you for taking the time to find those links, Reach4. I've found lots of apparently approved PVC and poly nipples there and elsewhere that are inexpensive till you add the shipping. I'm just trying to learn whether there's something about them that prevents Home Depot and Lowe's, who sell lots of PVC fittings of all kinds and filters that need nipples, from carrying them. Usually, but not always, if HD and Lowe's don't sell something that's as commonly needed as a nipple for a filter, it's because most people use something else, but in this case, that something else is a metal nipple into plastic, which is generally considered unwise.

 

[Reach4]

but in this case, that something else is a metal nipple into plastic, which is generally considered unwise.

I don't think that people generally think that using a brass nipple into plastic is worse than a plastic nipple into plastic.

I think you will not find anybody who recommends that the Big Blue filters sit on their sumps on the floor.

 

[Garn]

I don't think that people generally think that using a brass nipple into plastic is worse than a plastic nipple into plastic.

I think you will not find anybody who recommends that the Big Blue filters sit on their sumps on the floor.

Just a very quick sampling: in the following discussion on this forum, a plumber and a master plumber both advise against male metal into female plastic, the latter saying, "Avoid screwing metal male threads into a plastic female whenever possible." https://terrylove.com/forums/index.php?threads/pvc-to-brass.21640/

Why not have a Big Blue on the floor, or, in my case, on a shelf?

 

[Reach4]

Just a very quick sampling: in the following discussion on this forum, a plumber and a master plumber both advise against male metal into female plastic, the latter saying, "Avoid screwing metal male threads into a plastic female whenever possible." https://terrylove.com/forums/index.php?threads/pvc-to-brass.21640/

You correctly quoted the Redwood post. It is not totally clear that he likes plastic to plastic threads either.

I think you mis-read the Jimbo post. He said to not overtighten or over-tape, to my way of thinking.

Why not have a Big Blue on the floor, or, in my case, on a shelf?

Hard to change the cartridges. Sloppy.

I do have a big blue housing with GHT metal adapters on it. I use it for the recirculation water on the rare occasions when I sanitize my well. I did not buy the housing for the purpose, but ended up with an extra.

 

[Garn]

You correctly quoted the Redwood post. It is not totally clear that he likes plastic to plastic threads either.

I think you mis-read the Jimbo post. He said to not overtighten or over-tape, to my way of thinking.


Hard to change the cartridges. Sloppy.

I do have a big blue housing with GHT metal adapters on it. I use it for the recirculation water on the rare occasions when I sanitize my well. I did not buy the housing for the purpose, but ended up with an extra.

It would be great if Jimbo or Redwood sees this discussion and weighs in.

Something on the order of 10% of the reviews for this type of housing complain of leaks, mostly at the O-ring or the pressure relief button, but a good number say the housing cracked open. I wonder whether some of that cracking would trace back to overtightening brass into the plastic.

I've also read more discussions of plastic vs metal male nipples. Some say PVC isn't allowed indoors for potable water. One person said CPVC is allowed, but becomes brittle over time. I have found polypropylene nipples and haven't read anything negative about them.

I've been focused on shopping for fittings and connectors, so I hadn't given much thought to how to support the Pentek-type filter, and the other three filters are designed to sit on the floor, but I see now that the Pentek-type filter is changed by removing the bottom of the housing, so I'll hang it on its bracket. Thank you for making me think about that sooner.

 

[Reach4]

Something on the order of 10% of the reviews for this type of housing complain of leaks, mostly at the O-ring or the pressure relief button, but a good

You plan to use valves on either side. You might also consider a bypass. Otherwise a failed filter housing, rare as that is, could put you out of the action. ON my cartridge filters, I have valves. To bypass on an emergency basis, I can use a potable water hose around the filtering. One end would go on the drain valve at the pressure tank, and the other onto a boiler valve. Boiler valves are also able to mount a pressure gauge, and pressure gauges are good for identifying clogged elements. I also keep extra o-rings on hand. Usually they can be re-used, but if not, an o-ring with no spare that could not be reused (typically stretched so it will no fit back into the groove) could also put you out of action.

 

[Garn]

You plan to use valves on either side. You might also consider a bypass. Otherwise a failed filter housing, rare as that is, could put you out of the action. ON my cartridge filters, I have valves. To bypass on an emergency basis, I can use a potable water hose around the filtering. One end would go on the drain valve at the pressure tank, and the other onto a boiler valve. Boiler valves are also able to mount a pressure gauge, and pressure gauges are good for identifying clogged elements. I also keep extra o-rings on hand. Usually they can be re-used, but if not, an o-ring with no spare that could not be reused (typically stretched so it will no fit back into the groove) could also put you out of action.

Thank you. The instructions from the retailer call for shutoffs on each side, but I'm questioning whether they're needed, as the shutoff for whole house will be a few feet away. Can you think of any reason I would need the shutoffs? If I need to bypass this filter, I can use a nipple to connect the two female flexible connectors on each end of the filter directly to each other.

 

[Reach4]

A shutoff after the filters would keep the house pipes from draining out when you change cartridges.

 

[Fitter30]

Brass or stainless is for potable water. Like blue monster for telfon tape. Never had a problem with mixing material just don't get excited tighting. Big blue has a bracket that screws to the top of filter and not the piping.
Changing filter close supply open cold valve bleed pressure off before trying to unscrewing filter housing. Use 1 micron spun glass element change it twice a year on well water.

 

[Garn]

A shutoff after the filters would keep the house pipes from draining out when you change cartridges.

Thank you. I hadn't thought of that, as nothing will be higher than the filter, but it seems worthwhile in case there's enough water in positions where it might want to drain back.

 

[Garn]

Brass or stainless is for potable water. Like blue monster for telfon tape. Never had a problem with mixing material just don't get excited tighting. Big blue has a bracket that screws to the top of filter and not the piping.
Changing filter close supply open cold valve bleed pressure off before trying to unscrewing filter housing. Use 1 micron spun glass element change it twice a year on well water.

Thank you.