Rheem Marathon 80Gal Holding Tank

Finally had some time to install a holding tank for domestic hot water. Still have to finish the electrical work, but got the plumbing done and tested. It works great! Endless hot water for the wife's bath...

The output of the tankless is feeding into the hot water heater cold inlet. The output of the hot water heater is feeding back to the hot water feed for the house where the mixer is located. I still have the short connecting piece if I need to replace the hot water heater for any reason. Its on top of the EFM on one of the pics below.

I'll get my 9 tons of coal next week.

daluds wrote: Endless hot water for the wife's bath...

Did you run out of hot water running off the coil only ? Any thought of using a tempering valve to save the soft flesh body parts from scalding ?

He had a thread a while back about the tankless not being able to handle filling a soaker tub. I had the same problem with a 30 gallon indirect, so I hooked the tankless coil up in series with the tank.

He mentioned a "mixer", which I took to be a mixing valve. Regardless, scalding is pretty unlikely if he has the coil hooked up in series with the tank. i.e. Scalding water from the coil gets diluted in 80 gallons of water before making it to the tap.

markviii wrote:He had a thread a while back about the tankless not being able to handle filling a soaker tub. I had the same problem with a 30 gallon indirect, so I hooked the tankless coil up in series with the tank.

I have a 30 indirect and never have any problems with running out with the kids using the bath tub. The recovery rate is higher than my 80 gallon electric that has been sleeping quiet nicely for the last 10 months.

AA130FIREMAN wrote: I have a 30 indirect and never have any problems with running out with the kids using the bath tub. The recovery rate is higher than my 80 gallon electric that has been sleeping quiet nicely for the last 10 months.

What size is the tub? Have you ever measured the fill rate? My indirect has a greater recovery rate than a 80 gal. electric as well, but it still can't handle our larger tub and fast-fill fixture. It will handle our normal tub and back-to-back showers just fine.

Dave, do you have the 7 gpm coil in the EFM?

The tub is a 1960's 5 1/2', not all that large by todays standard. The fill rate is 4 gpm and it will keep up on the coldest winters day with my priority switch turned off on the circulator pump relay.

Hello All,

I do have a mixing valve to set the high limit temperature to prevent scalding. Also, my wife has a very large 80 gallon bath tub or soaking tub. Its ridiculous in size. The tankless while running on oil heats up fast enough to support the big tub, but with coal it takes too long for the fire to build up to keep the water hot. I have the larger 3/4" tankless coil for the EFM boiler, and it really pulls heat out of the boiler. I decided to go with the electric water heater since I was having a lot of out fires, but since adding the draft inducer I don't have any outfires. The Rheem Marathon is still a great holding tank/water heater since it has very good insulation properties and long life since its not made of metal.

Finally, have a great setup for my house. I still have to fix more stuff since the house was built so poorly. There is a lot of heat lost in the hot water pipes due to the builder placing the uninsulated hot water pipes directly against the AC duct work, and running the hot water pipes up the outside walls of the house. I get a big heat loss in the pipes on the 2nd floor of the house. Endless fixing.

Dave