Aight, we'll call the previous home owner Waldo. He was a jack of all trades... Who knew little and just "made things work" according to the neighbors.

I have a 50 Gallon 68000 BTU water heater as a boiler. 3/4 feeder lines into 1/2 tubes that run into the floor. Six cutoffs for six zones 2390 sq ft home. No bleeders for air, nothing but water in the system. No pressure valves, except the pressure release valve on the water heater. The home water heater feeds into the heating system and has a check valve after the valve. On the return is a pipe that can pe used to let water out of the system. Pump is a grundfos type UP 15-42 F.

So, the question is... How do I make it better, I know the water heater has to be replaced (it's almost 10 years old) but then what?

Regards,
Casper

I do know a fair bit about plumbing repair just not on a radiant heat system.

Lets start first by where is your home located, how many square feet is the home,what is the tubing type,and has this setup been able to heat your home.Does this water heater also serve the domestic hot water needs.To start a heat load calculation would determine the amount of btus needed to heat the space.From the calculations this would then determine the tubing size and lengths needed for each room or zone.You didnt mention if the tubing is in the slab or stapled under the floor joist. It is never a good idea to use the same water without isolating the radiant system by using a heat exchanger.

If it has been working okay for 10 years, why do you need to make it better? Are you not satisfied with how it is operating now? Why not just replace the old water heater?

As previously stated, dual purposing a tank for both the heating system and potable hot water supply is not recommended by many knowledgeable people.

If you want to learn about these systems the best book IMO is Modern Hydronic Heating by John Siegenthaler, P.E. Since your pipe is already encased in concrete, you cannot do much to improve/redesign your piping system. Do you have any info that defines the type of pipe, spacing, circuit lengths? If so, you could at least better understand the fluid dynamics and heat transfer capacity of your piping system. We have DIY analysis/design calculators on our website. Please carefully read the instructions before using the calculators.

Borst Calculators

Coincidentally, the illustrative pump performance curve in our hydraulic radiant floor heating design calculator is your Grundfos 15-42.

"As previously stated, dual purposing a tank for both the heating system and potable hot water supply is not recommended by many knowledgeable people."

Seriously? I have been designing radiant floor systems using every available heat source including hundreds of tank type water heaters for dual purpose space and DHW. This a common and very popular design here in Minneapolis and other cold climates. In fact we have several systems in San Francisco.
I should think they would fit most homes in the mild climes of Oregon as well. Contact us, and we will give you a hand. These are not to be confused with "open" space and DHW heating systems to which your broad statement would more accurately apply.