Tankless water heater guestion

[lati_cz]

I am building 5k sqft home for family of 5, with 5 baths.
Plumber (experienced, good and well established in our area) plumbed house for 1 tankless heater.
I questioned it, he said it will be enough and he put one in larger homes on regular basis without problems.
There was another plumber on site, he said we must have 2.
We can still re do plumbing for 2, but it involves resizing gas line, adding vent to metal roof, opening walls etc.
I do not mind, I want to make thinks right, but I do not want to add extra cost if not neccesary.
Please advice. Thank you, Michal

 

[Stuff]

First of all, why are you going with tankless? In most circumstances the drawbacks outweigh the benefits.

 

[Sponsor]

 

[Dj2]

Sizing a tankless water heater takes some calculations.
- You need to know by how many degrees you need to raise your ground water to the desired temp (from estimated 55 in your area to around 105 = 60 degrees). This is called temp "raise". Note: You must verify your ground water temp, the above is my estimate.
- You need to know how many gallons per minute you will be using, if for example you will have a shower, washing machine and dishwater running all at the same time. In this example a shower is 1.5 GPM, washer 2 GPM and DW 1.5 for a total of 5 GPM. Note: These are estimates only.
- you take this info and check with the tankless label to see if it meets your demand. In my example the demand is 5 GPM at 60 degree raise.

Once you know what WH you need, you will have an idea what else you need, like gas supply and vent.

 

[Plumber69]

I am building 5k sqft home for family of 5, with 5 baths.
Plumber (experienced, good and well established in our area) plumbed house for 1 tankless heater.
I questioned it, he said it will be enough and he put one in larger homes on regular basis without problems.
There was another plumber on site, he said we must have 2.
We can still re do plumbing for 2, but it involves resizing gas line, adding vent to metal roof, opening walls etc.
I do not mind, I want to make thinks right, but I do not want to add extra cost if not neccesary.
Please advice. Thank you, Michal

Put 2 in. You need it. Waste of money. Tanks are so much more reliable

 

[Dana]

A condensing tank type hot water heater big enough to fill the biggest tub with some margin is usually more satisfactory. You can get one with pretty big burner (even with modulating burners) if recovery time is expected to be an issue.

The Phoenix Light Duty with the 76,000 BTU/hr burner is enough to run a 24/365 single shower at Sunnyvale type incoming water temperatures, and the 80 gallon version can fill some pretty big soaking tubs. That would be more than enough hot water heater for 19 out of 20 five person families out there. If all five bathrooms have bath tubs (or the master bathroom is fitted with multiple gusher type side sprays), the 100 gallon PHM199-100 can support 2-3 continuous normal showers forever, and can fill a decent sized spa, all on gas service sized to support a single tankless.

 

[Master Plumber Mark]

If you were wise you would just install a 75 gallon Rheem gas hot water heater and live happily ever after.
In 10 -15 years from now you might have to replace it... no problem....

I already know that you simply will not be happy until you go with the hi-technology system that
will probably cause you nothing but troubles down the line.... and that could be a few months from now
when you notice it does not perform as well as you thought it would do...... Then your wife starts to complain
about sandwiching of hot and cold water......and you throw more money into the dark hole.

good luck and may god have mercy on your soul


here is something from another thread on this site.... this is what you have to look forward to.........

My wife and I just had our old water heater replaced with a Takagi
T-K4U-OS-N. When showering, I noticed the system tends to go from hot to luke warm to cool and then back to hot again. Also, when we initially ran a bath for our daughter, the water started out hot then just went completely cold and wouldn't come back. Now, this morning, my wife took a shower and the water went from hot to completely cold and then back to hot.

I've been doing research and want to see if I'm headed in the right direction. I set the water temp down to 115 from 120 as my first step (we live in California so it's not terribly cold but, the ground water in the morning is currently being measured at 60 degrees). I figure that could help with flow. According to the spec sheet from Takagi, a 55 degree rise means it can do about 5.7gpm. Which should be plenty to run our 2.9gpm shower (two heads) or our bath tub for our daughter (3.5gpm).

The other thing we're looking at is having PGE come out and upgrade our gas meter. It appears to be a 250CFH and we have quite a few gas appliances (dryer, stove, furnace + the new water heater). I'm guessing that's going to be way underpowered come this winter when we get the furnace going.

I'm also looking at having a recirculation pump installed but, not sure that's going to fix this particular problem. I saw in another thread here that this might also be caused by fluctuating water pressure from the city (we're on city water, not a well).

What do you guys think? Any help will be greatly appreciated. Sorry for the long winded post but, I wanted to get all the information on our system and location out so that you guys don't have to guess at it.

DustinH, Oct 3, 2016Re