Foaming beers: chronic infection or overcarbing?

I brewed a Belgian Tripel in June, bottled in late September. At the time, I was a little surprised to find it nicely carbed and delicious three weeks after bottling. Since then, however, that beer has tended to foam after each bottle is opened. Not. A gusher, exactly, more like the beer overflows 1-2 seconds after the bottle is opened. It still tastes great (maybe a little more banana ester than desirable, but nice maltiness) but as time goes on the foaming seems to be more aggressive with each bottle (stored and served at 50 degrees).

I decided to dump the batch, afraid that if the foaming is increasing then I might be risking bottle bombs.

Then I thought that I've seen this sort of foaming with other batches bottled since then. I opened a DIPA bottled in October, which sat for 5-6 seconds and then foamed over, and a steam beer bottled in November, which foamed pretty aggressively. I've been drinking these beers and have been happy with the flavor all along.

Do I have an infection that is carrying over from batch to batch but that I can't taste or have I been overcarbing?

I usually aim for the high end of the carbonation guidelines and let the beer carb in my furnace room, which is usually 70 degrees but can spike near 80 when the furnaces are going. I do countertop partial mashes and have about 15 brews of experience. The one change in my brew process that began with the Belgian Tripel in June was that I built a copper immersion chiller instead of using ice baths to cool the wort. I have probably been taking more gravity readings during fermentation as I gain experience but am good about dunking my siphon in starsan before taking readings.

So if I do have an infection should I dump all three batches? How should I
clean the bottles? I usually soak overnight in oxyclean, about 1.5 scoops per 5 gallons of soak water, then rinse and starsan.

Thanks for the help. I am confused.

How are you determining the amount and type of priming sugar?

I use aonline calculator. Was going for 2.4 volumes for the Tripel, so I used 4.4 oz of corn sugar.

I had a few batches do this early on and I think I was getting antsy and bottling too soon. If your beer isn't finished, by even a couple points, you still have fermentable sugar present in addition to what you're adding for bottling. Possibility?
I also wouldn't think your beers are infected if they taste OK.

2.4 is the high end of the range for 5 gals of a tripel, but 4.4 oz would get you there if you fermented at the high 70s towards the end. How are you measuring the sugar? Perhaps your scale is off. Try cutting back by 25% of what's recommended on your next batch, and see if you get to the right place.

Thanks for the input. I'm really hoping it's just overcarbing. I bottled a Belgian dark strong the other day and knocked the priming sugar down about that much. Hope that helps.

Its just over carbonation from the way you describe it.

I had a few beers do that. Most of them I primed on the high end and experienced them creeping up over several months before they stabilized.

I have a beer that's been foamy, but it tastes OK. I'm thinking one of two scenarios. 1st, I discovered my tubing was stained and I thought that maybe it infected the beer during bottling. 2nd, I added too much sugar, or it already had too much.

Today, as I was going through my equipment box I saw the recipe for the last batch. It said add 6 oz of corn sugar. Had I actually read the recipe and not just dumped the sugar package into the pot I may have held some back. I would never add 6oz of sugar, 5 would be the limit, 4 if I think it is a little sweet. The beer tastes just fine, just a little over-carbed, so I'm leaning towards the sugar.

Have you tried chilling them to 40F before opening them?

Yes, chilling overnight or so helps because more CO2 goes into solution.