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PaulSr
Hot Water Heater

Need to replace a 19 year old 50 gallon gas hot water heater. What are the pros and cons of going to the new tank less style or should I just install a new tank style unit. Our house has two and a half bathrooms and two people living here.

canuk
Re: Hot Water Heater

Tankless units have the advantage of taking up less room and can be energy savers. However, the common complaint is variations to the flow rate of hot water being produced. While they produce continious heated water many people are surprised when these units don't meet their expectation of large volumes of hot water.
The temperature of the cold water supply and the demand are main factors as to how much heated water these units will produce and supply. The colder the supply water is --- the longer it takes it takes to heat --- the less volume being supplied.
As demand increases this also limits the amount or temperature of the heated water the units can produce and supply.
It's very important to properly size these units to worst case scenerios.

Price of tankless units run at least 4 times the price of standing tank units.

Just some thoughts.:)

NashuaTech
Re: Hot Water Heater

I am in complete agreement with canuk's comments----in my opinion, well-stated and accurate.

sabo4545
Re: Hot Water Heater

I've had a Renni tank-less water heater for about 3 years now and for the most part love it. It has provided plenty of hot water (dish washer and showering at the same time). You can get them with different flow rates depending on your needs. My one main complaint would be that they are fairly noisy while running. I put mine in a closet near the upstairs bathroom. Currently I live alone so its not a big deal but I suppose if someone was sleeping while someone was taking a shower it might be a little loud. If its going to be in a basement this shouldn't be an issue however. As was stated they are considerably more expensive than a regular tank style water heater. They are however expected to last 25+ years that's usually a minimum of 2 regular water heaters but most likely 3. Then there is the savings in fuel costs since you are not heating water that you aren't using while out or sleeping. If you're staying in your house for a long period of time I would consider a tank-less. If you are planning on moving in a few years its probably not worth the extra money.

Mike

JLMCDANIEL
Re: Hot Water Heater

If you are talking about a gas unit, you may also have to install a significantly larger gas line.

If you are talking about electric, as an alternative you might want to consider a high efficiency WH like the Marathon WH.

Jack

sabo4545
Re: Hot Water Heater

Good point Jack, I didn't think to mention about the gas line. Tank-less water heaters that run on gas generally require a larger volume of gas while running than a tank style gas water heater. Mine is a propane model since there is no NG in my neighborhood.

Mike

thinksnowwhat
Re: Hot Water Heater

I recently installed a Reni on demand water heater...It takes an extremely long time to get hot water to my faucets, even the ones closest to the heater..I have upgraded 70% of the piping to 3/4 inch. And have upgrade the propane line and tank to handle the new volume. Any helpful hints on how to get hot water to our faucets quicker so we do not have to waste so much water?

Sten
Re: Hot Water Heater

On Demand water heaters are known to be slow at providing hot water, here's something I got from the Net.

A gallon of water will fill 63 feet of ½ inch galvanized iron pipe, 36 feet of ¾ inch galvanized pipe, or 20 feet of 1 inch galvanized pipe. In the case of type K copper pipe, a gallon of water will fill 88 feet of ½ inch pipe, and 44 feet of ¾ inch pipe.

This means that if you run your faucet at 2 gallons per minute, and you have 1 inch galvanized pipe, the water will travel 41 feet per minute. However, if you have ½ inch type K copper pipe, the water will travel 176 feet per minute, quite a difference. So the smaller the diameter of the pipe, the faster the hot water will reach the fixture, given the same flow rate.

Also I don't know what you did as far as upgrading your Propane Line but there are things that should be considered, BTU's, Length, pipe size. All this is measured in water column or the amount of pressure it takes to move a certain amount of water an amount of inches. With Natural Gas you should have 7 inches of water column on the incoming side and 3 1/2 on the manifold side, this is adjustable at the gas valve, (NOT TO BE ADJUSTED BY ANYONE THAT HAS NOT BEEN PROPERLY TRAINED TO DO THIS).
I believe the water column for Propane is 11 inches which could change if the pipe dia. has been altered but the sizing is done the same as NG but the nos. will differ. Any alterations that are done on NG or Propane should be done by a properly trained Tech

Just my two cents, I hope if someone has more info they will add to the post

canuk
Re: Hot Water Heater
Quote:

This means that if you run your faucet at 2 gallons per minute, and you have 1 inch galvanized pipe, the water will travel 41 feet per minute. However, if you have ½ inch type K copper pipe, the water will travel 176 feet per minute, quite a difference. So the smaller the diameter of the pipe, the faster the hot water will reach the fixture, given the same flow rate.

Wouldn't they both take 1 minute to supply 2 gallons ?

Sten
Re: Hot Water Heater

If your faucet is rated at 2 gallons per minute it will always give you that amount, but there is more water in a 1 inch pipe than a 1/2 inch pipe so the velocity of the water in a 1/2 inch pipe will be greater to make up the diff. It's all depending on the GPM rating of the faucet or showerhead.
In answer to your question yes, but the velocity is what makes up the diff.

sabo4545
Re: Hot Water Heater

I'm not really sure if a tank less water heater takes more time for the hot water to get to the faucet than a regular tank style water heater. Perhaps a little longer because it has to heat water that may be at say 55 degrees coming from the cold water side instead of room temperature water that is siting in the pipes and then the hot water coming from the hot water heater pushes it out. I do think however (and this is a guess) that the problem can somewhat lie in people's mindset. Many people that I talk to about my tank less water heater think that I have instant hot water at any given faucet. A tank less water heater is not a point of use heater (unless it is directly connected to a faucet) but a water heater that is just not heating water when it is not being used. So yes you may have to wait a little longer to get hot water but you are saving a good amount of fuel by not heating water that is not being used. If you are concerned about wasting water you may want to look into a pump that recirculates the water when a faucet is turned on until it is the desired temperature and then it will come out of the faucet. I have not personally used one but have seen them on Ask This Old House I thing.

Mike

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