what takes it so long

**DIY** · 01-08-2009, 02:09 PM

My house was totally re piped @ 4 months ago,and with that re pipe i decided to get a new water heater to (whirlpool "low boy" 30 gal capacity) no bells and whistles just your basic electric HWH. CPVC was used for the hot and cold sides inside the house tub/shower,bathroom sink,toilet and kitchen sink. The HWH is located in the kitchen and the hot and cold lines coming from it run along the kitchen wall under a counter top,and proceed out an exterior wall where @ 15' of pipe hot and cold runs underground and @ two 3' portions run along the outside of an exterior wall. All hot and cold lines either exposed or underground are foam stick insulated. Now the question. It takes a good 30+ seconds to get hot water when the tub or any sink faucet is turned on. Should i change the underground hot line portion to copper?,re trench the hot line and cover it with more insulation? turn up the thermostat on HWH... Advice,suggestions and remedys welcome.Thanks all!

**leejosepho** · 01-08-2009, 02:24 PM

Originally Posted by DIY

It takes a good 30+ seconds to get hot water when the tub or any sink faucet is turned on ...

That is an issue of flow rate and how much cold water has to be pushed out ahead of the hot water being sent into the line ...

Originally Posted by DIY

Should i change the underground hot line portion to copper?,re trench the hot line and cover it with more insulation? turn up the thermostat on HWH...

Those kinds of things can affect the temperature of the supplied hot water coming out of a faucett, but they will not change how long it takes for the hot water to actually arrive.

There are various types of recirculation lines that can make fully-heated water available almost instantly whenever a faucett is opened, and you might want to consider one of them. The simplest is a small pump under the farthest sink, and the cold line can be used as a return if you do not want to add a dedicated return line.

**DIY** · 01-08-2009, 02:39 PM

Thank you for the reply Leejosepho. I have wonderful water flow.Infact flow was one complaint i had before the re pipe. If flow seems to be the problem then what caused a re pipe to obstruct flow? Or are you saying to much flow now?... I'd like to learn more about this resurculation dedicated line or tank and how it works..? Thanks

**DIY** · 01-08-2009, 02:45 PM

correction: recirculation

**Dunbar Plumbing** · 01-08-2009, 02:47 PM

30 gallon electric water heater only provides 18 gallons of ready to use hot water.

**jastori** · 01-08-2009, 02:51 PM

Is it possible that your new lines have a larger diameter than the old lines?

This is generally a good thing (will improve flow). The downside is that it will take longer for the hot water to reach your fixtures.

If a faucet supplies 2 GPM (gallons per minute), and it takes 30 seconds for the hot to reach the faucet, then the pipes are holding 1 gallon of water.

If you upgraded your supply lines from 1/2" pipe to 3/4" pipe, for example, you would roughly double the volume of water stored in the pipes, and therefore double the amount of time that it takes the hot water to reach the faucet.

**leejosepho** · 01-08-2009, 02:52 PM

Originally Posted by jastori

Is it possible that your new lines have a larger diameter than the old lines?

This is generally a good thing (will improve flow). The downside is that it will take longer for the hot water to reach your fixtures.

Yes, that is what has happened.

**leejosepho** · 01-08-2009, 02:55 PM

Originally Posted by DIY

I'd like to learn more about this resurculation dedicated line or tank and how it works..?

Do a search for "recirculation" right here on Terry's boards and begin reading!

**DIY** · 01-08-2009, 03:08 PM

Good point Jastori. Most of the re pipe is upgraded to 3/4" CPVC inside and T's off to the shut off valve in 1/2" pipe. That answers some other questions to... Anyway,with that now known,is a recirculation line and/or pump the only way to fix this wasting water till hot water is available? Thank you

**Nate R** · 01-08-2009, 03:33 PM

Originally Posted by RUGGED

30 gallon electric water heater only provides 18 gallons of ready to use hot water.

Please explain. Is this because the remaining 12 gallons are diluted with incoming cold water? Is it different for a 30 gal gas heater?

What about a 40 gal tank?

I ask this because: We have a 30 gal gas heater now. We have installed a deep tub. (32 X 60 X 20) I'd guess the hot water is at about 130-140 degrees, and we don't get the tub full up to the overflow with a person in it before running out of hot water. It's close enough that I'm hoping upgrading to a 40 gal will be enough to get the tub filled. (Don't really have room anywhere for larger than a 40 gal)

**jadnashua** · 01-08-2009, 04:31 PM

A big tub could hold 80 gallons or more (the spec sheet for your tub would say how much it holds). Now, depending on the WH thermostat setting, you normally don't use only hot, you mix it with some cold. The hotter the WH is, when mixed with cold, the more 'warm' water you can get to fill the tub. But, because you are replacing the hot water in the tank with cold, even though hot rises and you are inserting the cold at the bottom, you'll never be able to empty the WH and expect it all to be hot. Thus, depending on the design, you may only get 70-80% of the volume of the tank as hot before the incoming water cools it off, especially at a tub filler which can flow possibly 5-15gpm, depending on the size of the supply pipes and the valve used. Think how long it takes to heat a pot of water on your stove, then think about 5-15 gallons/minute and you can see you either need a LOT of heat, or a bigger tank. If you look at the spec sheet for the WH, it will tell you how much hot water you can get out of it. Some WH have higher power heaters to help extend the hot supply, but they cost more.

**DIY** · 01-08-2009, 05:42 PM

In ways this does not make total sense to me yet,but just thinking aloud here.Would replacing any of the 3/4" hot side CPVC pipe with 1/2" CPVC be advantageous to getting hot water faster at any of the fixtures.

**jadnashua** · 01-08-2009, 07:28 PM

That might cause the pressure balance valve to lock up...

**jimbo** · 01-08-2009, 07:38 PM

There is a " 70%" rule which applies to water heaters, gas or electric. In short term analysis...i.e. during a shower......you can get 70% of the gallon capacity of the WH, still at a temp within 20º of set point. Yes , this is due to mixing of cold in as soon as you start to draw. For a 30 gallon tank, this gives a figure of 21 gallons. Obviously, set point and groundwater temp affect this, but the 70% rule is a good starting point.

**Dunbar Plumbing** · 01-08-2009, 07:54 PM

Originally Posted by Nate R

Please explain. Is this because the remaining 12 gallons are diluted with incoming cold water? Is it different for a 30 gal gas heater?

What about a 40 gal tank?

I ask this because: We have a 30 gal gas heater now. We have installed a deep tub. (32 X 60 X 20) I'd guess the hot water is at about 130-140 degrees, and we don't get the tub full up to the overflow with a person in it before running out of hot water. It's close enough that I'm hoping upgrading to a 40 gal will be enough to get the tub filled. (Don't really have room anywhere for larger than a 40 gal)

Any water heater, no matter electric or gas that is a tank type heater, the amount of water it takes before there's "significant" temperature drop is 12 gallons of water.

So, a 50 gallon heater would be 38, 40 gallon would be 28, 30 being 18.

Cold water displaces the hot to get the hot to leave the tank...at some point it will start tempering the water's temperature in doing so.