I have a staple up underfloor system with large tubes that don't contain an O2 barrier (brand is Radiantech, in VT). The first 10 yrs, had a steel propane boiler. The internal tank rusted out twice. Second 10 years had fairly efficient gas water heater (sealed combustion). That is wearing out now. What to do? I don't want to trash another boiler, do I just replace the water heater every 10 years? Also have iron, etc in water so smaller heat exchangers get fouled. No problem with water heater.

As you likely know, the problem with non-O2 barrier PEX is that it allows O2 to enter the system which results in corrosion of ferrous components. If O2 can’t enter the system, corrosion of ferrous components is greatly reduced. This is why O2 barrier PEX should always be used with a HR heating system.

If you don’t replace your non-O2 barrier PEX with O2 barrier PEX, the only solution you have is to only use non-ferrous HR components (e.g., brass, stainless steel) in your system. Using good water and corrosion inhibitors may help a little, but ultimately the corrosion will still win if O2 gets into the system and there are ferrous HR components. If you decide to replace your non-O2 barrier PEX with O2 barrier PEX, you should also consider a different HR emitter approach. In terms of efficiency and performance, under-floor staple up is as bad as it gets.

yeah if I knew 25 years ago what I've known for a while now...would have done things differently. It is a big tube with plates and works almost all year at less than 120 deg. I'm thinking 10 more years from a new water heater. The other option to go with stainless, etc is possible. I know the iron etc in the water tends to foul delicate items, I did clog up several plate heat exchangers before I gave up on that. So I'm a little hesitant to buy a fancy condensing boiler only to screw it up way before its life should be over. Is my thinking defective?

Good boilers are usually stainless, so that shouldn’t be an issue. You should also make sure all the other components are non-ferrous too. That plus refilling system with good water and inhibitors should serve you well. Ten years with a cheap water heater isn't bad ROI either.

can you mention some examples of 60 - 80K condensing boilers, stainless heat exchange (LP in this case) that you think are durable? That would be helpful to look at and price. thanks!

Hi,
We run in to this often, there is a desire to use tankless water heaters as a heat source, non seem to hold up as well as a boiler system.
#/4" pipe on a staple up that also seems like a total head ache to install compared to 1/2" runs. not sure why radiant tec designs that way.
We have been designing and installing some 30 plus years so i am only slightly opinionated.
As to boilers there are a lot of combination units with stainless systems, we sell LAARS products and prefabricate pump systems of all sorts. However I think the internal pump is a iron unit.
If your system basically works you might consider as Borst suggest swapping to all non ferrous.
Start with Potable water expansion tank, stainless grundfoss alpha pumps, and a simple LAARS all stainless wall mounted on demand water heater.
If you need it preassembled on to a simple panel we have that configuration.
Good luck
Dan

Hi,
We run in to this often, there is a desire to use tankless water heaters as a heat source, non seem to hold up as well as a boiler system.
#/4" pipe on a staple up that also seems like a total head ache to install compared to 1/2" runs. not sure why radiant tec designs that way.
We have been designing and installing some 30 plus years so i am only slightly opinionated.
As to boilers there are a lot of combination units with stainless systems, we sell LAARS products and prefabricate pump systems of all sorts. However I think the internal pump is a iron unit.
If your system basically works you might consider as Borst suggest swapping to all non ferrous.
Start with Potable water expansion tank, stainless grundfoss alpha pumps, and a simple LAARS all stainless wall mounted on demand water heater.
If you need it preassembled on to a simple panel we have that configuration.
Good luck
Dan

will look at lars, thanks. about the pipe size I meant the pex tubing is 3/4" or a little more. headers are 1" and 3/4"