Hayward Heater Header Union Nut wont Thread on

[Slash308]

Disassembled the unions on my Hayward H400 to replace the o-rings since one was leaking. Outlet union nut went on fine. Inlet won't thread on. It keeps jumping off on one side or the other, resulting in a crossthreaded connection. Anyone ever had either the header or the nut go out of round? What obvious thing am I doing wrong here?

I'm about at my wits end on this one since the original installers glued everything together in ultra-tight bends so the filter is only a few inches away from where I'm trying to work. If that nut is bad, then I have to replace my filter inlet male nipple, the whole assembly of elbows and pipe, and the union as well. All the elbows are close-fit so there's no spare pipe in between where I could cut, slip on a new nut, and re-join with a coupler.

 

[Slash308]

After checking with a dial caliper, the nut is out of round by 0.06 inches. It's slightly oval-shaped. How does that happen?

In any case, the only show in town (Leslie's) doesn't have one in stock. Tried calling to check before going over there, but no answer. Walked in the door, and found out why. The only clerk in the place was sitting behind the counter on the phone with his girlfriend. He never did hang up or put the phone down while telling me they don't stock Hayward parts. No wonder why brick-and-mortar places are getting eaten alive by e-tailers.

 

[duraleigh]

What is an H400? What is the diameter (roughly) of that nut?

 

[Slash308]

It's a Hayward heater. Model number is H400IDL. Roughly 3" diameter nut for Hayward's 2" PVC union that mates up to the heater's header/manifold.

At this point, I'm hoping that the threads on the header are still ok. Replacing the header looks like a couple hours of not fun work.

 

[duraleigh]

I got ya' now. I wasn't sure which piece of equipment we were talking about.

.06 out of round, IMO, should thread just fine. If you see no visible damage to the threads, I think your OK in that it will "round back up" if you can get it started.

I have messed with unions a few times and I noticed that the two mating surfaces must be darn near perfectly parallel and level. I'm sure you checked that the 0-ring was seated correctly but it might not hurt to recheck.

I had several failed attempts until I realized the two surfaces were just slightly askew and it would never start. YOu may have to apply some pressure to gently force the mating surfaces to parallel but I hope it will thread right up for you if you can do that.

 

[Slash308]

Upon closer inspection, the threads on the header are "cut-in" from being cross-threaded previously. It is on the bottom-side where I couldn't see until I laid on the ground to look after feeling something that wasn't right. No wonder why that nut was on there so tight. Gotta love running right into someone's previous damage. That would also explain the nut being trained out of shape after sitting like that for over a year. The nut will not thread onto the header by itself without the union flange. I cut the pipe in a place where I'm pretty certain I can use a coupling.

Ordered a 2-pack of new nuts overnighted. Added enough bleach to pool to bring it to 17ppm, since the system is plumbed pump-filter-heater-cell, with no bypass. That means I have no pump or filter until the heater is re-assembled.

I see a few options:
1. Do nothing and try to thread on the new nut, hoping it straightens the threads.
2. Hand file the threads on the header, shaving off the misshapen split-ridge area.
3. Replace the header, with the realization that it may go deeper into the can of worms I opened.

Wondering if I should order a new header and gasket. There's a lot mounted into that header. Sensors, relief valve, .... Ugh.

This would be a non-event if some place nearby had parts.

Little background: bought the house with the pool already installed about 18 months ago. Every time I go to repair something with the system, I seem to spend some extra time and money re-doing something that wasn't right the first time.

Classic example: ordered Polaris rebuild kit since only one wheel was powered. Upon disassembly, I found the main supply tube was glued(looked like 3M 5200) to the bottom base and the glue had completely swallowed a few of the other little fittings for the tail and back nozzle.

 

[duraleigh]

I like option number two but you are there and can see the extent of the damage. Sounds like it might work.

 

[ps0303]

This issue happens to me more times then not and is a common issue. Just start threading it on and it should fix itself. Just note that if it starts to get too tight and it's not on all the way, undo it and start again. I've spent 10 minutes at times on just one of them but I was able to get it on. Sometimes I would start it by turning it in the opposite direction until I felt it short of click and then spun it in the right direction.

Don't file it or make any changes like that or you will ruin it and probably have a leak. Just take your time and try to not get frustrated.

 

[Slash308]

New nuts are the exact same size as the old ones.

These should be 3 1/2" 8UN thread. That would be a thread with a minor internal diameter(nut) of 3.3647" and minor external diameter(bolt) of 3.3512."

First a disclaimer, I work in steels and sometimes aluminum. My tools don't really allow me to measure or cut properly into plastics. My calipers that are certified-calibrated have fairly sharp measurement edges, so I can't measure plastics beyond 0.001" or so. A squeeze of the calipers will embed the measurement edges into the plastic, throwing the measurement off by at least 0.001", maybe 0.003". If I attempted to use a portable threading machine on the header, it would just chew it to pieces. Same for the nuts; tried using a die on one of the new nuts to cut the threads bigger. The nut's threads didn't look too healthy after.

Measured out, the new nuts are 3.333." Old nut is 3.334"

Header (bolt) is 3.375"

So the nuts are 0.0317" too small in basic minor diameter, and the header is too small by 0.0238" The total difference is 0.0555", which is huge in machinist terms. It's like trying to fit a coke can inside another coke can. No go. It's a wonder any of these ever go together. I've seen this a few times on Chinese junk that comes in for work. 3.375" and 3.333" are produced when you screw up rounding the dimensions in the CAD program. 1/3=0.333 and 3/8=0.375.

 

[Slash308]

GOT IT!

Gloves are recommended. Standard precautions for hot water or cooking should be followed.

1. Keep the header as cool as possible. Cold, wet rags or even ice packs placed on the header are a good way to go, especially if it's a hot day or if the sun is shining directly on the black header.
2. While the header is chilling down, place nut in boiling water for several minutes. Carefully carry boiling container outside. Don't take the nut out of the hot water until your are ready to use it. It will cool very quickly.
3. Screw the nut on. It should go on very easily.

The hotter you can get the nut and the colder you can get the header, the better. The bigger the difference in temperatures between the two, the easier it will go on.

Other effect of heating the nut is that the PVC has a bit more flex when it's warmed up, so the threads conform to each other more easily.

 

[ps0303]

Heating also makes things easier to cross thread. I wouldn't suggest what you have done. All it takes is time and patience and the unions will fit just like they are supposed to.

 

[Slash308]

All I can say is it worked, it threaded on very easily, it does not leak, and it's not cross-threaded.

I do think it's disappointingly low-quality fabrication work on a $2000 heater that something as simple as a union won't marry up smoothly. It doesn't do a lot for my confidence in the quality rest of the unit.

 

[BernardB]

Those Union nuts are very finicky to say the least. I have had mine off twice in the last month. I ended up marking the universe n nut where the thread begins with a sharpie. I lined up the mark with the point on the head where the thread begins. On one of them, you could feel it pop into place, similar to one of the posts above. The other seated solidly with evenly placed force. Patience and even pressure are the ticket.

 

[stevecherifi]

GOT IT!

Gloves are recommended. Standard precautions for hot water or cooking should be followed.

1. Keep the header as cool as possible. Cold, wet rags or even ice packs placed on the header are a good way to go, especially if it's a hot day or if the sun is shining directly on the black header.
2. While the header is chilling down, place nut in boiling water for several minutes. Carefully carry boiling container outside. Don't take the nut out of the hot water until your are ready to use it. It will cool very quickly.
3. Screw the nut on. It should go on very easily.

The hotter you can get the nut and the colder you can get the header, the better. The bigger the difference in temperatures between the two, the easier it will go on.

Other effect of heating the nut is that the PVC has a bit more flex when it's warmed up, so the threads conform to each other more easily.

You sir are brilliant. I just created an account just so I could reply with my thanks. I almost spent $100 on new unions (crazy local pool store likes to upcharge) and I was thinking I needed a new plastic manifold but I tried your boiling the nuts tip and it threaded on PERFECTLY and EFFORTLESSLY. I never was so happy to boil my nuts. Thanks again sir!

 

[swamprat69]

Replaced my header gasket last year. Found that the header union nut was extremely hard to line up correctly because of the very fine thread on the header union. If your piping into the union is at all out of square, it is almost impossible to make the connection without cross threading it. Finally I cut the piping going to the header union and made the connection at the header with the piping disconnected while using a PVC union where I cut the piping as the last connection because the PVC union has a much coarser thread.

 

[swamprat69]

Also if you cut both the header inlet and outlet piping so they both have PVC unions, you can make a U shape bypass that you can install if the heater is out of service for any length for water side cleaning or service.

 

[Jackelope]

You sir are brilliant. I just created an account just so I could reply with my thanks. I almost spent $100 on new unions (crazy local pool store likes to upcharge) and I was thinking I needed a new plastic manifold but I tried your boiling the nuts tip and it threaded on PERFECTLY and EFFORTLESSLY. I never was so happy to boil my nuts. Thanks again sir!

Disassembled the unions on my Hayward H400 to replace the o-rings since one was leaking. Outlet union nut went on fine. Inlet won't thread on. It keeps jumping off on one side or the other, resulting in a crossthreaded connection. Anyone ever had either the header or the nut go out of round? What obvious thing am I doing wrong here?

I'm about at my wits end on this one since the original installers glued everything together in ultra-tight bends so the filter is only a few inches away from where I'm trying to work. If that nut is bad, then I have to replace my filter inlet male nipple, the whole assembly of elbows and pipe, and the union as well. All the elbows are close-fit so there's no spare pipe in between where I could cut, slip on a new nut, and re-join with a coupler.

This is an extremely annoying problem with these union joints and I’ve spent hours trying to align threads. Here’s what I’ve discovered works for me: smear a little silicone lubricant on the stem threads. Mark the start of the threads on the cap with a marker or piece of electrical tape on the outside of the cap. Align the mark just before the start of the thread on the stem. Turn the cap about half a turn. The cap will misalign. Using an adjustable width pair of pliers, gently compress together the cap and stem on the opposite side to your mark. The cap will pop into alignment on the threads. You should now be able to spin the cap on the rest of the way by hand. Best part: no need to boil your nuts!