pvc unions any good?

[sherrod624]

I'm plumping up my well house water supply w/ pvc. Somewhere long the way of life I was raised to have a disliking for pvc unions. And because of that I have never used any. How do you guys feel about pvc unions? I'm going to use a brass tank tee after the pump. would it be worth switching from pvc to a brass union with a male adapter and then back to pvc?

 

[aka Larry]

A brass union seals via the threads right? A PVC union seals via an o-ring, which we use on our pool pump setup, and it works quite well.

 

[Jon_E]

I use PVC unions on all my pool fittings, never had one leak.

 

[readhead]

I just put a new PVC union on my pump last week and it works fine. I changed the pump and had to rework the piping. The old system had a PVC union in it for the last 15 years and never had any trouble.

 

[rlitman]

A brass union seals via the threads right? A PVC union seals via an o-ring...

Brass unions do not seal via the threads. They seal via metal mating surfaces.

PVC unions seal via an o-ring.

I've got nothing against PVC unions. If the system is already PVC, I'd say go with them.

Just remember the usual issues when dealing with o-rings. Have proper o-ring lubricant available and use it any time the ring is re-exposed.

 

[Cyberbear]

I've used PVC unions with mixed results. Some have been fine while others have failed to seal properly, so it's all up to you I suppose. Also, I've never had any long term success with PVC ball valves, they all seem to fail sooner or later by not operating after years have passed and you suddenly need to shut down a pipeline.

 

[glentre]

Likewise, I've had pvc unions in my pool lines for many years with no problems. And, they get opened every year for winterizing and closed again in the spring.

Glen

 

[mrobins297aaa]

have them on my pool also, maybe 5 years, no problems

 

[pattenp]

If using PVC pipe use PVC unions. I have a bunch of PVC unions in my sprinkler system valve boxes to simplify the removal of valves for repair and have never had any issues with the unions. Even got them on my backflow preventer so to remove it in the winter.

 

[rharman]

Since it's a well, I guess I'd be OK with PVC. Constant pressure, like from a water main, would cause me to worry too much.

In fact, I just had to replace a shutoff to our sprinklers and a hose bib and opted to not use a PVC union just due to the constant pressure.

 

[nine4gmc]

I have PVC unions on my air lines for easy replacement of the busted lines after they explode.

No, I keed.

 

[Shiftless]

hahaha Nines

 

[ddawg16]

I would only be concerned if the pressure was high.

I have PVC unions on my water sprinkler system...no issues.

One question....is it going to be exposed to the sun? If so, I wouldn't use them....

 

[Sawdustmaker]

I would only be concerned if the pressure was high.

I have PVC unions on my water sprinkler system...no issues.

One question....is it going to be exposed to the sun? If so, I wouldn't use them....

Ditto!

 

[JerryB]

We just completed (yesterday) a complete rebuild of a two tank filtration and treatment plant that supplies water to our small rural subdivision. All Sched. 80 PVC, mostly 2". There are nearly 20 PVC unions in the new piping, which replaces 30+ year old steel piping.

The system incorporates 4 x 3 way motor driven ball valves. Each of those valves uses 3 PVC unions. Additional PVC unions are used at points that might require disassembly in the future. All our large diameter unions have either a silicone or neoprene o-ring. We started the system and had only one very small leak: One of the unions was only hand tight!

The thing I do avoid in systems employing both metal and plastic piping is threading metal male fittings into plastic female fittings. Too many split fittings over the years, especially if some inexperienced person does the tightening! As an example, our water treatment plant employs a number of 2" brass check valves and brass gate valves used as manual flow controls. These all have female threads and we use PVC male pipe x socket adapter (to transition back to PVC pipe) fittings on these.

We also re-built our pump stand a few years ago, eliminating virtually all the metallic fittings. Again, the chosen material was 2" Sched. 80 PVC, with several unions to allow disassembly to replace pumps or valves. The pump stand is outdoors, subject to all kinds of temperature fluctuations as well as some vibration from the 2 x 10 HP electric pumps. No problems at all.

 

[Cougar]

How high of pressure can they handle.

 

[mrobins297aaa]

I would only be concerned if the pressure was high.

I have PVC unions on my water sprinkler system...no issues.

One question....is it going to be exposed to the sun? If so, I wouldn't use them....

just curious, why not?

 

[slip knot]

Sunlight will degrade plastic. We paint any exposed PVC at work. I also use the PVC unions without issue. The valves when exposed to chlorine don't seem to last very long. The valves on my water well at home are at least 10 yrs old and still work fine. No cl2 there.

 

[JerryB]

How high of pressure can they handle.

There are several on-line charts showing pressure ratings and other factors. One thing to be aware of is that PVC is affected by temperature, and the working pressure is derated.

See: https://www.commercial-industrial-supply.com/documents/schedule80-pipe.pdf

For example, 2" Sched. 80 at 120°F is rated at 400 psi. This drops to 160 psi @ 120°F.

As written above, it also (very slowly) degrades in sunlight. We too paint any exposed pipes, but most of our outside piping is also covered by foam insulation.

 

[Cougar]

There are several on-line charts showing pressure ratings and other factors. One thing to be aware of is that PVC is affected by temperature, and the working pressure is derated.

See: https://www.commercial-industrial-supply.com/documents/schedule80-pipe.pdf

For example, 2" Sched. 80 at 120°F is rated at 400 psi. This drops to 160 psi @ 120°F.

As written above, it also (very slowly) degrades in sunlight. We too paint any exposed pipes, but most of our outside piping is also covered by foam insulation.

Are the unions rated to the same pressure? I only need about 70psi.

 

[JerryB]

Are the unions rated to the same pressure? I only need about 70psi.

Yes, the standard fittings are rated the same as the pipe they go on. PVC Unions have O-rings, making them really easy to seal as compared with common steel pipe unions.

I just came back from spending several hours at our rebuilt plant. We couldn't get any back flush flow out of one of the filter tanks. After quite a bit of time looking at valve positions, water pressure, etc., we decided it must be an obstruction in one of the back flush pipes.

We took apart a couple of the PVC unions on the 1-1/2" back flush line. To our total surprise, the check valve in that section was backwards! The nicely machined brass check valve body was marked with etched arrows which we carefully followed. Once we could see into the pipe, we realized that the etching on the outside of the valve was reversed! That along with the etched label: "Made In China!"

Two strikes against our supplier in the last week: Last Wednesday we were assembling the area where the new plumbing hooks into the old tank outlets. We couldn't get one of the new 2-1/2" galvanized ******* to thread into an existing female coupling. Once we gave up and got out from under the tank, we looked at the ****** in detail, fully expecting to find a damaged thread. Not so: The thread on one end of the ****** was left hand. Really difficult to see the tiny hash marks that delineate left hand threads!

To answer your original question, PVC unions are great so long as they are installed properly and protected from large external forces and the sun. And remember that we only use Schedule 80 pipe and fittings.

 

[rharman]

I would only be concerned if the pressure was high.

I have PVC unions on my water sprinkler system...no issues.

One question....is it going to be exposed to the sun? If so, I wouldn't use them....

I'd have no problem with them on the outbound side of the sprinkler valves but would not use on the inbound side under constant street pressure.

 

[JerryB]

<snip> . . . but would not use on the inbound side under constant street pressure.

Why is that?

We have lots of 2" Sched. 80 PVC pipe on our outdoor pressure pump platform. At least 6 unions on the pressure side (average pressure is ~90 psi) and they have been there since we rebuilt that part of the system about 5 years ago. The only special thing we did was to paint the exposed pipe. These unions make it easy to remove a pump in the event service is needed.

Our two 10HP pumps keep line pressure (between 75 and 100 psi) on this piping 24 hours a day, 365 days / year.

They are designed for this service. Way better than the rusty galvanized pipe they replaced!

 

[JRC3]

This 1" PVC union sees 65psi. I broke it apart to install the cycle stop valve a few months ago with no issue. I do use silicone grease just in case.

 

[JerryB]

The pix shows Schedule 40, not Schedule 80. Way weaker. It also appears that the piping is under a significant amount of stress due to the routing and connections it is supporting. PVC (especially Schedule 40) is NOT hose, and should not be treated as such. It needs to be straight and supported, not just bent to fit. Even more so with Schedule 40.

IMO, that is a poorly carried out installation.

 

[tymbo]

This 1" PVC union sees 65psi. I broke it apart to install the cycle stop valve a few months ago with no issue. I do use silicone grease just in case.

what is your opinion on the cycle stop valve? Worth it?

 

[sherrod624]

I too would like to know what you think about the CSV as my PVC union instillation is for a CSV

Jerryb

To the right of the CSV in that pic is pex.



Sent from my iPhone using Tapatalk

 

[JRC3]

Yes it is pex. I didn't have a 1" crimper When I first installed the new plumbing or I would've went pex. I have something I want to change up top and when I do I'm gonna scrap the pvc for pex.

I got the CSV because I didn't like my pressure drops (30/50) especially after it had to pass through my iron/sulfur filter and softener. After I installed the CSV with a gauge on the well side, I saw that pressure gauge sitting near 80psi so i decided to crank my pressure switch up to 40/60. When I did the well side pressure went down a little so I decided to utilize that pressure on the house side so I went 45/65 and it sits around 74 before the CSV. IMO the new higher pressure makes the CSV not as needed for pressure drop problems (the main reason I bought it), but it definitely does what it's most designed to do...Stop cycling. I do like the consistent pressure especially since I have two shower heads.