Used Woodmaster 4400 Questions

The biggest problem that I have experienced with wood boilers, although none outside boilers . The problem is trying to match the heating load to the continuous output of any wood boiler be it indoor or outside .
I believe as the technology of wood burning exists today , the best way to equalize the load to output problem is to use heat storage . Sizing a wood boiler to burn a full charge of wood at full output and have the fire burn out at the same time that the heat storage tank achieves full temperature or close to it .
I have operated a none gasification boiler connected to our 1,000 gallon storage it burned 10 cords per year .This same boiler burned 16 cords per year without storage!
Our gasification boiler ( 30 + year old Jetstream) connected to the same 1,000 gallon storage , with the same load only burns 4 1/2 cords per year .
I have never seen a Hardy but what I have drawn from this forum on the longevity of outside wood boilers , as rule their life span is not much more than 10 years .The nature of a fire in a firebox surrounded by water is that the fire cannot burn very hot and with this same cool water jacket becoming caked in creosote , the moisture between creosote and the steel being corrosive and in turn eating through the steel .

I forgot to welcome you to "Hearth" in my last post ,so welcome
On the OWB make sure that it is allowed by the local authorities in your area , in many places even phase II outdoor units are disallowed
Myself I believe that most boilers can benefit by adding storage.
The heat loss from storage in your basement may or may not contribute to a noticeable amount of heat loss into your basement it all depends on how well your storage is insulated . Our boiler with a well insulated storage are in a separate insulated below grade room in the basement . In the summer we can go as much as 20 days between firings when just drawing DHW ,at the end of the 20 days that room will be around 55 degrees .

Personally, I would not touch a used OWB of any kind - 8 years is really getting up there for some of them. And when they do go seriously wrong, there is no simple replacement of parts to fix them - they are scrap.

Exactly what 'maintenance' did he do? And what is he replacing it with?

I have to admit - I have no experience with outdoor boilers.

But replacing with fresh water each year would also introduce a bunch of fresh oxygen. Maybe the conditioner has the covered, but if he didn't get it right there could have been internal corrosion slowly going on all those 8 years that won't be evident until it is too late.

A friend of mine had to replace his Wood Doctor after only 4 years, it turned into a pile of leaky scrap. Not all are equal, but I hate seeing things like that happen to people.

Definitely doesn't reflect the risk.

non-barrier pex in your slab isn't an issue with a non-pressurized OWB. It will require a heat exchanger if you run a pressurized unit.

If you thought your high efficiency fireplace churned thru wood, wait till you get an OWB! I'm sure my fireplace insert can heat my house on less wood per year than my gasser. OWB is going to compare very poorly.