Will larger water heater increase hot water time?

Discussion in 'Water Heater Forum, Tanks' started by Jakobkraft, Sep 14, 2009.

  1. Jakobkraft

    Jakobkraft New Member

    Sep 14, 2009
    New Jersey
    I'm a first-time homebuyer, just recently bought a 900 sq ft condo.
    There are two bathrooms - one right next to the water heater room and one on the opposite side of the apartment. The shower closest to it gets hot water in less than a minute, but the shower on the other side of the apt. takes maybe 5 minutes before the water turns hot. The pressure is very good so I don't think there's anything clogging the pipes.
    The water heater is a 30 gal A.O. Smith which is over 12 years old and only gives hot water when the thermostat is set to 'Very Hot', which, I thought, shouldn't be necessary. I called A.O.Smith and they told me that over time the thermostat core can wear out and so I should replace it eventually, even though it hasn't started leaking and still gives hot water.
    My question is: if I got a larger unit - say 40 gal or 50 gal - would that make the water turn hot faster for the shower that's further away? Or is it simply the age of this unit which causes it to take so long to heat water a moderate distance away?

    Thanks in advance for any info!
  2. jimbo

    jimbo Plumber

    Aug 31, 2004
    San Diego, CA
    No. Your problem is not related to the size of the tank. It is the distance. All the cooled-off water in that long pipe has to run out before the hot water from the tank arrives at the shower. There are retrofit recirculation systems to deal with that.
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  4. Cass

    Cass Plumber

    Nov 12, 2005
    Jimbo is right...the length of time it takes to get hot water is directly related to how the piping is run and the heat exchange with the copper...all that determines how long before you have HW at the faucet.
    Last edited: Sep 14, 2009
  5. Jakobkraft

    Jakobkraft New Member

    Sep 14, 2009
    New Jersey
    Sorry to be such a noob, but what is a retrofit recirculation system and how I can I get it?
  6. Dana

    Dana In the trades

    Jan 14, 2009
    It involves a pump and a length of plumbing between the remote bathroom and the heater to pump hot water toward the bathroom, returning the cooled water that is being displaced back to the tank (rather than down the drain.) When the hot water arrives at the bathroom it automatically switches off. Some systems cycle on/off continuously, others utilize a flow sensor and only turn on when there's demand for hot water.

    google [hot water recirculation system], to learn all the particulars.
  7. Gary Swart

    Gary Swart In the Trades

    Sep 1, 2004
    Yakima, WA
    There are at least 2 types of recirculating systems. One requires a separate line between the most distant hot water outlet and the tank. There is a small pump that is located near the tank. The pump can operate 24/7 or be on a timer. The other type does not require a separate return line and is the easiest retrofit in most cases. Another factor to consider in the delay time to purge the cold water from the lines is the size of the pipe. A 3/4" pipe contains much more water than a 1/2" line of the same length so the delay is considerably longer. Once you have a recirculation system, you will wonder how you ever lived without it.
  8. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Sep 2, 2004
    Retired Systems engineer for defense industry.
    New England
    One of the simplest recirculation systems to install is the RedyTemp unit (if you have an outlet to plug it in). Should take all of about 5-minutes to install.

    Mine has been working fine for about 5-years now.
  9. Scuba_Dave

    Scuba_Dave Extreme DIY Homeowner

    Jan 5, 2009
    Used to be in IT
    South of Boston, MA
    Condo, so no basement/attic?
    IE can you insulate the water pipe going to the other side?
    That will help with heat loss while running, but not the time it takes to purge the cold water & heat up the pipe

    We went from a 30g to a 50g & the length of time we have HW has increased
    Plus I insulated all the HW pipes
    Copper pipe used to be cold about 12" above the HW heater
    The new HW heater came with a 2' section to insulate the pipe
    I put it in & checked about an hour later - the pipe was now hot at the end of the 2' insulation
    So I bought more pipe insulation & did the whole thing

    My wife's old condo had the HW running thru the slab Then along a cold wall to the kitchen - so it took longer for the water to get hot in the kitchen.
    If your pipe to the other end of the house runs in the concrete that will be another heat loss
  10. Jakobkraft

    Jakobkraft New Member

    Sep 14, 2009
    New Jersey
    Yes, no basement or attic.

    It looks like the best, and simplest solution will be the RedyTemp unit.

    Thanks all for the info!
  11. Thatguy

    Thatguy Homeowner

    Aug 27, 2008
    A bounty hunter like in "Raising Arizona"
    Having reached 12 yrs you have a 50% chance of it making 16 yrs, assuming it's a gas heater.
  12. Runs with bison

    Runs with bison Member

    Aug 23, 2009
    As others have said, the difference is the length (and possibly diameter) of the pipe runs. Have you actually timed them? That's not meant as a wise-acre question, but I would be very surprised if it took anywhere near that long in a 900 square foot living space. If it does take several minutes then it might be worth tracking down why.

    It might have an overly large diameter pipe run in that long leg. Bigger is not better unless you want a lot of flow with low pressure drop. Shower flowrates are not that large so they should be fine with 1/2" lines and still acheive negligible pressure loss. Larger means a lot more cold water to clear and a lot more pipe to warm before the shower comes to temperature.

    Another factor is what flowrate showerhead is installed in each bath? If you have a truly low flow showerhead (as in ~1.5-1.6 gpm) in the farthest bath then the warm up time will nearly double versus the standard 2.5 gpm showerheads...that are now misnomered as "low flow." I've got one of the new truly low flows in the master shower and it has increased warm up time to ~45 seconds (measured...and it seems like a long time), whereas before the 2.5 gpm warm up was short enough that I only had to wait about 20 seconds.

    If instead you have one of the old showerheads it could be 5 - 10 gpm. I still had a 5 gpm showerhead (bucket tested) in a previous home a few years ago. A home inspector was commenting how he liked his old 9+ gpm Waterpik (he had bucket tested it) but also accepted that he ran out of hot water rapidly with it.

    The polyethylene pipe insulation is really inexpensive (roughly $1.50 for 6 feet) so if you have access to the pipe runs you can fit that yourself to the runs. It won't eliminate cold water in the lines so there will still be the cold purging delay, but it does seem to speed warm up and keep the water slightly warmer at the tap (e.g. when you want full hot.)

    Another thing you can do to deal with long warm up is install a thermostatic shower valve such as the Ladybug. It won't change the warm up time, but can make it easier to deal with. You turn on your shower (best it so turn it to full hot) then go about your business. When the water temp hits ~95 F the valve closes to a minimum stop, allowing a small amount of water to trickle out. Pull a cord/flip the valve and you have full flow again without wasting any appreciable amount of water in the meantime. It resets itself everytime you actually shut off the water.

    Some are keen on recirculation systems, I have no experience with them. The idea of a push button operated one that recirculates on demand does sound appealing since they should come without additional heat loss and actually conserve some water that goes down the drain during warm up. On the other hand 24/7 or thermostat controlled ones seem like money wasters/energy hogs to me, so I would opt for on demand recirculation.
  13. hj

    hj Master Plumber

    Aug 31, 2004
    Cave Creek, Arizona
    hot water

    The retrofit system most are referring to NEED an electrical outlet in the cabinet under the sink and most bathroom sinks DO NOT have such an outlet. The Grunfos Comfort, and other similar ones, install the pump at the water heater and use a "thermostatic valve" at the sink to control the water temperature. Two advantages to this system;
    1. you do not have to replace the pump when the thermostatic valve wears out.
    2. You usually have an outlet near the water heater or close enough so an extension cord can reach it, and the cord would not be as unattractive there as it would be in the bathroom.
    There can be other reasons for the thermostat not being accurate, but the "core wearing out" is not one of them.
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