More hot water

niles_lishness · May 1, 2014

Briefly, owner of resort home heavily used during ski season feels there isn't enough hot water for all the skiers to shower at end of ski day. He thinks a second water heater would be solution, but I'm having a few misgivings.

Existing heater is Rheemglass Power Vent 2 75-gal 75000 btu gas-fired unit. I have been told one cannot hook two gas-fired units in parallel with no real explanation other than " you can't do that." So, wondering if there are alternatives to solve issue.

I have identified these strategies: 1] replace existing tank with larger one, say 100 gal; 2] supplement existing with an electric heater in series in front of existing; 3] install an on-demand wall mount heater either in series or parallel. Each of these have pros and cons, so could use some guidance.

Thanx in advance

phishfood · May 1, 2014

What does your plumber say?

journeyman · May 2, 2014

I am having a hard time understanding why you cannot hook up to heaters parallel. I service commercial properties that have tandem heaters. You just have to make sure the water draw is the same so one heater is not working harder than the other. As long as you have enough room, gas supply and venting i dont see why you cant. If possible elaborate why you cant or what you are being told

niles_lishness · May 2, 2014

Sadly, Phishfood, it is one of the plumbers from whom I am soliciting bids that has told me I cannot hook them up in parallel. It was another one who suggested it in the first place, hence my confusion.

There certainly seems to be enough room to accommodate an additional heater - utility room has two outside walls for venting. A 1-inch black iron pipe supplies natural gas at city pressure [ 4 oz I believe ] but local utility indicates they can bump that up at regulator, if necessary. House load is currently 290k btu, between cooktop, two furnaces and fireplace, but local utility also indicated that wouldn't be an issue.

Wonder if parallel installation of new heater next to existing one would present problem balancing the work load. Seems if there was sediment load, pipe scale or blockage, one heater would be doing all the work and situation would not necessarily be improved.

Maybe a heater set to 100 in series in front of the existing heater would be best path, cutting down on recovery time during high demand. City water comes out of tap at 51, so it's a heavy lift to get to 120.

Grateful for any additional thoughts.

journeyman · May 2, 2014

You have to pipe them evenly to diplace work load

SHR · May 2, 2014

Two heaters are often used together. Parallel is not the best installation though. Maybe that is what the second plumber meant or they are not a real plumber and do not know much about plumbing. Search the forums, there are many excellent threads about the best ways to install 2 water heaters together.

journeyman · May 2, 2014

Maybe i am using the wrong word. I call it a tandem set up. You have to heaters together and the water piping is the same distance from each heater so they work the same amount of time. Or you might be able to install a storage tank that works off the water heater and that way you have 150 gallons of water instead of 75.