Traveling to Pompeii from Naples on a Sunday

Circumvesuviana trains run every day. https://www.sorrentoinsider.com/en/naples-to-sorrento-train-schedule.
No reservation possible (or needed).

Choose Porta Nolana or Garibaldi (lower level of Napoli Centrale) as your departure station from Naples.
Arrive at Pompei Scavi - Villa dei Misteri.

Walk about 100 meters to Pompei entrance/ticket office.

Hi Anthony -
Using the Trenitalia website and next Sunday's date, a LOT of Metropolitano trains from Napoli Centrale/Garibaldi to Pompei station come up, and tickets are running only 2.80 euro or so. They do not need to be purchased in advance, and they do need to be validated before boarding.

For Pompei> Salerno trains - also Metropolitano or Regionale and tickets are also very cheap - input both stations into the Trenitalia website for your date.

Understand that if you're going from Naples to SALERNO, you will be using different trains than you would if SORRENTO was your final destination. The FS Pompei station on the Salerno route (and yes, spelling of that station is correct) is in the town of Pompei and 1/2 mile/15-minute walk or so from the nearest entrance to the scavi, which would be Piazza Anfitheatro. The Naples> Sorrento route trains, however, stop just outside of the Porta Marina entrance. Both have luggage storage....which you're going to need if traveling onward to Salerno. There might be storage at Pompei station but someone else will have to weigh in there. You can probably take a cab to the Piazza Anfitheatro entrance if not up for the walk.

http://pompeiisites.org/en/pompeii-map/info/

The Pompei train station is pretty small and I doubt it has a luggage storage facility. I don't recall seeing one when I passed through it. It's probably best to use the free luggage storage at the Porta Marina entrance to Pompeii. After your visit, you can take a short cab ride to the Pompei train station to catch the regional train to Salerno. The last Sunday regional train to Salerno departs at 9:36pm.

Edit: Let me rephrase my comments, which are based on my personal experience. I've twice used the luggage storage at Porta Marina and thought the service was great, so I can highly recommend it. I've used other entrances but have neither used nor noticed luggage storage at those locations, so I can't make any recommendations regarding them. I've walked between the Pompei train station and the Pompeii site, and I suggest not doing so with luggage in tow. Some sections have no sidewalks and busy traffic, so I recommend a taxi instead of walking.

Frank, as they have to go onward to Salerno anyway, I was thinking why not just go to Pompei station to begin with? My guess is that the train from Naples to that station might be more comfortable than the Circ. to Pompei Scavi-Villa dei Misteri station (in front of Porta Marina)? If they'd have to cab it from that entrance to Pompei station for the onward journey to Salerno, well, 2 short cab rides to/from Piazza Anfitheatro (or just one, if willing to walk it one-way) wouldn't be much different than 1 longer one from Porta Marina? I'm also thinking that entrance is more lightly used/not as busy.

Just to confirm, there is "cloakroom service" (bag storage) at all entrances so luggage isn't an issue at Piazza Anfitheatro.

http://pompeiisites.org/en/visiting-info/visitor-services/

Ideally, if FS Pompei station had luggage services, storing it there, taking a cab to the Porta Marina entrance, exiting the site at Piazza Anfitheatro and either walking or taking a cab the short distance to the Pompei station could be a good plan too but without knowing about storage....

Anthony, make sure you are not confusing the Trenitalia service to three stations in MODERN Pompeii, with the CIrcumvesuviana commuter-transit line that stops on the opposite side of the ancient site, at Pompeii Scavi-Villa Misteri. There is luggage checking at all entrances to the ancient site, but you want (I think ... ... or you imagine .... ) entering at Porta Marina (ancient site, most popular entrance), and leaving on the side that has a +- 1 mile trip to the Trenitalia stations for Salerno.

You may wish to re-plan the entire transfer, based on the actual rail services. No one here has ever reported a problem with the ancient-site's bag checking. I also suggest that you try to visit the excavation first thing in the morning, when it is not so hot, and the sun is not so high. I realize that this does not fit your sketch of the day.

This is not your precise issue, but reading it may be helpful:
https://community.ricksteves.com/travel-forum/italy/pompeii-salerno-capri-recommendations

There is a Circumvesuviana line ( NAPOLI-SCAFATI-POGGIOMARINO) which stops at POMPEI SANTUARIO station (yes, there are multiple stations in Pompei) further north of the FS station - near Santuario della Beata Vergine del Rosario - but no trains from that one go to Salerno.

https://www.eavsrl.it/web/sites/default/files/eavferro/NAPOLI%20SCAFATI-POGGIOMARINO%20L4.pdf

Thank you to everyone on this thread for providing helpful information! You have confirmed that the train does run on Sunday, which is a relief. I am also realizing that my plan to bring bags to Pompeii and further on to Salerno may be an unnecessary complication that will kill time better spent visiting the site. I am thinking I should revise my plan: Instead, we'll use Naples as our base. From there, we can visit the archaeology museum in Naples, visit Pompeii, and then come back to Naples before catching a Naples-Salerno train in the morning.

Anthony, your ending post is a fine one.
My wife and I arrived at Naples and went directly to Pompeii for the day and then to Salerno for 4 days.

In my reading, only the Porto Marina entrance had luggage size lockers.
They worked well.
After the long day of walking Pompeii, it was a long walk w/ luggage to the Pompei station for the train to Salerno.

So going back to Naples is a fine choice.

P.S. Salerno was a very nice city to walk around. Not touristy, moderate size Italian.

Post-trip note: As it turns out... we ended up doing a hybrid of what I described above. We traveled from Naples to Pompeii on the (hot, packed) Circumvesuviana train with our bags with no trouble. There was an inconsiderate, lively pack of teen males that boarded the train just before Pompeii Scavi, but we pushed through them without incident. We stored our bags at the Pompeii Scavi train station with no trouble - they have a manned room for luggage - €12. When we returned to the station, we planned to get a taxi to the downtown Pompeii station, but we saw no taxis. Fortunately, one of the official station people negotiated with one of the many parked tour buses to give us a ride for €10. That's the biggest taxi I've ever taken! Instead of staying in Naples or Salerno that night, we ended up catching trains to our next destination, staying there the night.
Note: We spent 4 1/2 hours in Pompeii, following the Rick Steves 1-hour walking tour, but we didn't finish the tour. Pompeii is awesome! Water bottle tip was awesome; and the running fountains of drinking water kept us well hydrated. Rick Steves really brings Pompeii to life; I'm so grateful for the guidebooks for that. Although Pompeii is not a pile of rumble (it's actually in amazing shape), it is a large site of stone building after stone building. However, upon reading the walking tour as we visited, each building came to life, providing wonderful insights into daily life in ancient Pompeii. Thank you, Rick Steves!

Nice to hear from you, Anthony, and that your excursion was a great success! Yep, the scavi is quite a place, isn't it? :O)