Why do I keep cracking the ports on my multiport valve?

[kakerlak]

I replaced our pump and was up and running for about a week and then noticed the (Hayward) valve cracked at both inlet and return fittings. Kind of chalked it up to old brittle valve body and/or me overtightening the pipes into it and bought a brand new valve.

The new one I deliberately assembled much looser -- didn't even touch it with the pipe wrench. And, again, I was up and running for a few days with no issues, only to find it cracked and dribbling again. We have had some overnight freezes and have had the pump running at 1500rpm during those spells.

I'm hesitant to swap it out a third time for fear of the same result. Pipes in are normal 1.5" white PVC and I've been using Rectorseal Tru-Blu thread sealant. Really did not come even close feeling like I was forcing anything the second go-round.

 

[ajw22]

Are you sure the unions are Hayward made to fit the MPV you are using?

I would skip the Rectorseal Tru-Blu thread sealant that a search shows has PTFE. Pentair has a label on some MPVs saying to use Plasto-Joint Stik only and not Teflon paste or pipe dope on the threads. Pentair also says to tighten hand tight plus 1 1/2 turn’s maximum.

The "Do's and Don'ts" of Assembling Threaded Plastic Fittings from Lasco Fittings provides a great explanation of the Do’s and Don’ts to not have threaded fittings crack.

For more see PVC Repair - Further Reading

 

[JamesW]

The multiports are usually ABS plastic, which is more brittle and weaker than other plastics and the female threaded ports are not thick enough and they split too easily.

There are also usually mold marks on the ports, which might create weaker areas.

It's a defective design, in my opinion.

 

[kakerlak]

The second time around, I just hand tightened everything and could've probably cheated an extra half to three-quarter turn into them with hand strength. (So like hand tight, minus .5-.75 turn, lol).

Do you think the thread sealant was just a bad choice? What's a better option?

 

[kakerlak]

Here's some quick pics

I'm almost wondering whether the first time was overtightening + brittle old valve body and second time was just not running the pump fast enough for the freeze. It seems to have cracked a good few inches laterally across the valve body itself, although that crack does run into the threaded port.

 

[1poolman1]

Here's some quick picsView attachment 478050View attachment 478051

I'm almost wondering whether the first time was overtightening + brittle old valve body and second time was just not running the pump fast enough for the freeze. It seems to have cracked a good few inches laterally across the valve body itself, although that crack does run into the threaded port.

Though that fitting is too far into the valve, it isn't what cracked the valve body. It wouldn't put stress on that portion of the valve.
Looks like some sort of upward pressure to crack like that. Was the pipe coming out of the top of the pump just "a little too tall/short?" Next time get some 1.5" hi-temp pump unions. They do thread all the way into the body as the threads are not tapered like a pipe thread. They seal with an O ring against the body.

 

[bradgray]

Though that fitting is too far into the valve, it isn't what cracked the valve body. It wouldn't put stress on that portion of the valve.
Looks like some sort of upward pressure to crack like that. Was the pipe coming out of the top of the pump just "a little too tall/short?" Next time get some 1.5" hi-temp pump unions. They do thread all the way into the body as the threads are not tapered like a pipe thread. They seal with an O ring against the body.

+1

 

[kakerlak]

Though that fitting is too far into the valve, it isn't what cracked the valve body. It wouldn't put stress on that portion of the valve.
Looks like some sort of upward pressure to crack like that. Was the pipe coming out of the top of the pump just "a little too tall/short?" Next time get some 1.5" hi-temp pump unions. They do thread all the way into the body as the threads are not tapered like a pipe thread. They seal with an O ring against the body.

Man, thanks!

Actually, no, I didn't notice having to strain them into line. But those fittings are something I didn't know existed and seem like a better setup for this anyway! And, knowing nothing about pools before we bought this house, I asked the guy at Leslie's when I started this project if there were pool-specific fittings and he kept telling me everything for pools is just overpriced PVC and just get regular PVC pipe and fittings from Lowe's.

 

[Bperry]

Man, thanks!

Actually, no, I didn't notice having to strain them into line. But those fittings are something I didn't know existed and seem like a better setup for this anyway! And, knowing nothing about pools before we bought this house, I asked the guy at Leslie's when I started this project if there were pool-specific fittings and he kept telling me everything for pools is just overpriced PVC and just get regular PVC pipe and fittings from Lowe's.

If the multiport is not setup for tapered pipe fittings then it’ll crack if you install tapered fittings.

 

[kakerlak]

If the multiport is not setup for tapered pipe fittings then it’ll crack if you install tapered fittings.

Yeah, that's kind of why I asked them about that -- I expected there to be fittings specific to some of this stuff. If that thing was untapered inside, it might explain why the tapered pipe ends screwed so far in without resistance, only to end up cracking the fittings. The only tension they'd have at all would be from just that last/widest bit of thread.

 

[Bperry]

Yeah, that's kind of why I asked them about that -- I expected there to be fittings specific to some of this stuff. If that thing was untapered inside, it might explain why the tapered pipe ends screwed so far in without resistance, only to end up cracking the fittings. The only tension they'd have at all would be from just that last/widest bit of thread.

Another reason not to go inside a pool store. Maybe try the Hayward fittings instead or at least look for the parts drawing and see if it has a note about the fitting specification. If it says a size like 1.5”, 2” and then folllws with “NPT” then those are the tapered pipe threads. If it uses an o-ring to seal then the threads are not tapered and home depot fittings won’t work.

 

[PoolStored]

@kakerlak What does this sticker say?

 

[kakerlak]

@kakerlak What does this sticker say?

View attachment 478132

I thought I was doing exactly this. I will say that even approaching one extra turn with the pipe wrench felt like overnighting, so the first time was like hand tight, plus maybe a half turn and second time was hand tight, somewhat shy of how tight I could've done by hand and it still cracked. The "how tight" and references to thread sealant actually suggested to me these were tapered fittings. The paperwork in the box was pretty minimal, mainly just personal injury warnings and warranty info -- no real installation instructions beyond the same instruction about hand tight + 1-1.5 and to use thread sealant.

 

[JamesW]

In my opinion, the fittings are too weak and crack too easily.

Also, there is no such thing as "Hand-Tight".

Unless there are numbers and units, it's not a real metric.

For example, three minutes or three meters are real measurements.

 

[kakerlak]

In my opinion, the fittings are too weak and crack too easily.

Also, there is no such thing as "Hand-Tight".

Unless there are numbers and units, it's not a real metric.

For example, three minutes or three meters are real measurements.

100 percent. I wish this valve body was made out of the same sort of uncrackable fiber infused plastic that the pump body is, especially since it's a stressed member every time you press down and turn the lever on top, which takes considerable force.

But I never even turned the valve on the new replacement -- just hooked it up, observed it running without dripping and left it alone for about a week of regular off and on pool running, then it cracked.

 

[duraleigh]

Also, there is no such thing as "Hand-Tight".

I have used "hand tight" all my life and find it usefully descriptive.........just like "snug" or "firm"

 

[Newdude]

It took me 5 or so years to realize my hand tight was tighter-er than the PBs who installed my equipment originally. I spent many a spring chasing leaks. In hindsight, I'm a big dude who was young at the time and the PB was retirement age and slightly less strapping. But whattayagonnado?

 

[JamesW]

There really is not a torque that can be specified because the sealant lubricates the threads.

What you would need to measure is the pressure exerted by the male fitting into the female fitting causing compression in the male and tension in the female.

The torque cannot be reliably converted into a compression and tension reading.

In some cases, “hand-tight” is the best way to describe something.

However, if you had 100 people do something “Hand-tight”, you would get 100 different results.

The difference from the lowest to highest might be 10 times or more.

So, it’s a situation where it takes experience and some degree of skill to know when the fitting is tight enough.

 

[JamesW]

In my opinion, manufacturers should give torque specifications for all items requiring a torque to install or at least a minimum and a maximum for different conditions.

The terms “hand tight”, “finger tight”, “Snug” etc. are vague and inexact.

I have used these terms and I will probably use these terms again because I don’t have torque specifications for most applications.

The terms are useful for people who know what they mean.

There is an art and a science to getting the correct torque even when you have a torque specification and a torque wrench.

Some people have a good understanding of these terms and a good feel for how tight to make different things from screws, bolts, nuts, fittings etc. and some people don’t.

Hayward, Pentair and Jandy do provide a few torque specifications for a few things, but for the most part, they do not provide torque specifications.

https://hayward-pool-assets.com/assets/documents/flowcontrol/pdf/iom/FLVPIOM.pdf

https://www.pentair.com/content/dam/extranet/nam/industrial-flow-technologies/flow/ift-asset-library/pool-spa/S285(10-15-04).pdf

https://www.jandy.com/-/media/zodiac/global/downloads/h/h0576700.pdf

 

[JamesW]

In my opinion, the manufacturer should also give a list of all suitable sealants with the preferred sealants listed as preferred.

There is no reason that a manufacturer cannot give a precise and exact process for making a good secure leakproof seal that will hold up over time and not crack or damage the equipment.