The water is never in contact with the ash zone, or basically you can torch off the ask system and weld it back on new and not touch the water jacket at all, talked to a few that have done just that in fact and were very pleased with being able to do just that to a old boiler.
While touring the plant I talked to the workers and fabricators doing the actual work, a very knowledgeable bunch that do top notch work, from a welding and fabricating standpoint.
I don't know if they still make them, but at one time they made forced air wood burners that you set out beside your house and piped the hot air in, there are a few of those still going in my area, the people seem to love them.
A few of the local repair shops that repair all makes of wood furnaces and boilers recommend them to customers, mainly because they give product support and if their is an issue that's no longer covered by warranty, the local shops can call and get help and answers as to how go about fixing or repairing one of their products, even if they are 30 years old, most of the rest of the companies won't do this, I'm told.
All in all, people are happy with their products and their products last a long time, is what my research has found.
Before jumping the gun and buying any boiler before laws kick into place, call and talk to the folks at Arch Alloy and ask point blank, are they going to be in business, and what if any changes they'll have to make to their product to continue building owb's, the last time I did, they told me they were not too worried about it.
I'm a pessimist by nature, so I'm going to wait it out and see who's left in the industry to deal with, whatever I buy this time around, I hope is going to be a good company dedicated to meet whatever challenges and law changes and still be there decades down the road to serve customers and their needs, not like the last company I bought an owb from.
I should have bought one of royal's boilers the last time, but didn't do my homework good enough beforehand, I feel they are a good company, with a great product and will be here decades from now, guess time will tell if I'm right or not.