Needed: Hot H20 For Spa

fred lupton

We are building a custom home shower/spa that will have 4 body sprays and 2 shower heads (one is a rain head 2.5 GPM min) that will be able to put out 12 gallons per minute of 105 +/- degree water when on full. Or put another way about 9 GPM of 120 - 130 degree H2O. The owner wants to be able to have full capacity on demand but realizes the limitations of getting enough hot water. We are looking at Rinnai
tankless in series or AO Smith Cyclone Xi and Vertex. The boss also wants to be able to be able to have other family members use the shower immediately afterward with little or no wait time. Our plumber says to just use two 50's with a re-circulating system. Any suggestions on how to do this without going overboard?

Double-A

You're talking about lots and lots of hot water there and you're never going to get it from two 50 gallon water heaters. (You get 70% of volume with a 30 degree drop in temperature on a standard 50 gallon heater with 40K BTU input, so... 75 gallons total hot water / 9GPM = 7.5 minutes of shower time.)

The recirculation system just cuts down on the delivery time of the hot water, it has no effect on how much hot water you can deliver to the shower.

Also, all of the plumbing to the water heater, from there through the mixing and diverter/distribution valves, must be able to pass your 9 gallons/minute or all of this is for naught.

BTW, your shower heads are rated at 80 psi. If you don't have 80 psi delivered to them, they won't deliver that much water.

Contact your water purveyer and find out what the average water temp is for the year and what the low water temp is. Measure the pressure available to the house and contact a plumbing engineer or the technical service departments of your favorite water heater companies.

I hope your client has a wallet as big as his dream shower. He's gonna need it.

Also, don't forget...

• If you go commercial on the heater, you'll need a big (possibly huge) vent.
• If your heater is a condensing unit, you'll need a drain and a trap primer.
• If its natural draft, you'll need make-up and combustion air supplied to it. You might need a very heavy duty stand, depending on location of heater.
• You're going to need a big gas meter (can your purveyor supply a meter this big in this area of town?).
• You're going to need big gas lines to this heater and/or pressure regulators if your gas purveyor puts in a high pressure meter and you run a high pressure gas system in the house.
• Is your water service and water meter sized to run this shower and say, the dishwasher/washing machine/garden hose at the same time?
• If you must have backflow prevention and/or pressure regulation, you're creating a closed system and will require expansion tanks or pressure relief to protect the system from damage.

This is a short list off the top of my head. I'm sure there is more to think about.

Also, your plumber has to be a consummate pro on this job. Don't hire Billy Butt-Crack or your client will think about suing you and Billy and hire a hit man instead. These are the types of jobs and separate the real plumbers from the posers.

Good luck.

__________________
"My clients’ wishes are the center of my attention." -- David Guido, a contractor in Woodstock, N.Y.
New York Times, July 20, 2006

Michaeljp86

One thing you could do is use tanless heater, you may need 2 of them and have a recirculating system. But you would have the recirculation come on from a motion switch when someone walks in that way the hot water will be instant.

fred lupton

Thank you guys so much. Your input is greatly appreciated. We are meeting the gas company in an hour to start the process of upgrading the gas supply.
All of your other cautions and suggestions are appreciated and added to my check list. - Thanks! I'll be back in touch. Have a great day.

kevjob

Rinnai can be linked together to give you what you need but they get exoensive.

__________________
Kevin
Basement Finishing Highlands Ranch Colorado
Littleton Colorado, Basement Remodeling
Kitchen Remodeling Denver

Mike Finley

I have that exact same set up in my own house. 4 body sprays and two shower heads (everything is 2.5 gal by the way unless it is bootleg).

I have (2) 50 gall gas water heaters hooked up in series with the old one set at about 100 degrees feeding into the the new one which is a fast recovery unit about 2 years old.

I can run everything on full blast and crazy HOT for at least 30 minutes before it starts to get cold.

The situation I'd be most concerned with in a set up is water pressure not hot water.

KillerToiletSpider

One Takagi Mobius 1 tankless water heater.

__________________
A flush is better than a full house.

fred lupton

Thank you for your responses, I am very grateful!

Our water pressure is controlled to 75 psi, we can adjust it.
Our 4 body sprays are 1.8 GPM each with the restrictors left in. That requires 7.2 GPM,

Add either the rain head (2.5) or the hand held shower (2.5) and
we are just under 10 GPM.

Assume about 80% hot water at 130 degrees F ? That is 8 GPM actual but certainly may fluctuate so I'm going a little higher for comfort, safety and fluctuations in the water supply temperature.

I'm sharing all your comments with our owner as we go through our checklist. We are using a skinny plumber here, no Billy Butt-Crack!

You guys are awesome, Thanks