Question about plumbing design

[Victor Hastings]

Hello!

I'm an armchair architect hoping to design & build a house in a few years. I have a question about water supply design.

I don't like waiting for hot water, & I've tried recirculating pumps without much success. I want to design my next house to minimize the wait.

One idea I've had is to plumb the house for cold water only (PEX pipe), & heat water at the points of use, using a small tempering tank followed by a tankless water heater.

That layout would be tough to retrofit on an existing house, but it would be easy to design from the ground up.

Would a system like this work?

Thanks.

 

[Terry]

So how many tankless water heaters are you planning to have?

 

[Sponsor]

 

[Jeff H Young]

Recirculating systems work great, if you've completely designed and piped a hotwater system that didn't work very well and don't see where you went wrong then you just need a little help . instant or near instant hot water is a luxury is not free but worth while in my opinion it almost seems cheap its so nice!

 

[Victor Hastings]

So how many tankless water heaters are you planning to have?

Hi Terry,

Given the house layout I have in mind, I figure three locations need hot water: master bath, powder room & kitchen.

The primary washer/dryer hookup will be in the master bedroom walk-in closet, using the master bath hot water supply. It wouldn't have instantaneous hot water, but that doesn't matter in a laundry room.

I would put a secondary w/d hookup in a closet by the kitchen, plumbed to the kitchen hot water supply. I probably wouldn't use that hookup, but a subsequent buyer might decide that they prefer to lug dirty clothes to the other side of the house, wash & dry them there, & lug them back to the MBR.

The powder room would need only enough hot water for hand washing, so a small (2.0 gpm) tankless heater without a tempering tank would probably suffice.

 

[Victor Hastings]

recirculating systems work great, if youve completly desighned and piped a hotwater system that didnt work very well and dont see where you went wrong then you just need a little help . instant or near instant hot water is a luxury is not free but worth while in my opinion it almost seems cheap its so nice!

To me, instantaneous hot water isn't a luxury, it's a necessity. I hate wasting gallons of water every time I open a faucet.

I love the idea of a recirculating hot water supply, & I've retrofitted three pumps onto three problematic hot water systems -- but the results have been disappointing.

I'm building this house from scratch, so I can design for tankless heaters & tempering tanks at every point of use, with no dedicated housewide hot water lines.

Or, I could install a housewide hot water recirculating system, using a single high capacity heater feeding insulated pex pipe.

The nice thing about a distributed system is that a failure in one part of the house doesn't affect the rest of the house, whereas a whole house system that depends on a single HWH is 100% screwed if that unit dies.

And the cost of insulated pex pipe throughout the house is also a consideration.

Thanks for responding!

 

[Jeff H Young]

Id go with a recirc system. 3 water heaters dosent make sence to me, youll still be wasting water waiting for the hot water because a tankless has cold water and it takes longer to get the hot water.
a single water heater dosent nessesarily have to be high capacity

 

[Victor Hastings]

Id go with a recirc system. 3 water heaters dosent make sence to me, youll still be wasting water waiting for the hot water because a tankless has cold water and it takes longer to get the hot water.
a single water heater dosent nessesarily have to be high capacity

Hi Jeff,

My thought is to use a small tank heater (like Bosch's 2.5 gallon model, about $160) to preheat the water for the tankless unit. In the kitchen, I'd use something like Rheem's RTEX-18 ($410).

I just realized that I can put the half bath powder room near the kitchen & pull hot water from there. So I'd need only two tank/tankless heaters.

Do that make better sense?

Thanks for your input.

 

[Tuttles Revenge]

Install a proper hot water recirculating system supplied from a Single source water heater either a storage tank or 199kbtu tankless.

Tankless electric water heaters are terrible. You would have to have a dedicated 240v line to each and a dedicated 120 to the small tanks.

If you just needed that in One location it might be ok... but not in every spot in your home, its just a bad idea.

 

[Victor Hastings]

QUOTE="Tuttles Revenge, post: 701973, member: 67567"]Install a proper hot water recirculating system supplied from a Single source water heater either a storage tank or 199kbtu tankless.

Tankless electric water heaters are terrible. You would have to have a dedicated 240v line to each and a dedicated 120 to the small tanks.

If you just needed that in One location it might be ok... but not in every spot in your home, its just a bad idea.[/QUOTE]

 

[Victor Hastings]

Okay, I'm convinced. By "a proper hot water recirculating system," I assume you mean a closed loop system with a dedicated return line? All of the recirc pumps I've installed just push warmup water into the most remote cold water line, & they never work well.

Thanks for the advice.

 

[Jeff H Young]

Okay, I'm convinced. By "a proper hot water recirculating system," I assume you mean a closed loop system with a dedicated return line? All of the recirc pumps I've installed just push warmup water into the most remote cold water line, & they never work well.

Thanks for the advice.

Yes that's what I think a loop back to the water heater. The other way that you installed isn't as good but I put a few on like that and wasn't disappointed it was still worthwhile but wouldn't ever plan it that way

 

[Tuttles Revenge]

When building new or having a signifigant portion of a home open during remodel, a dedicated return closed loop should always be installed. If designed correctly I like to target hot water in under 5 seconds to every fixture. On a project I was working on for the State of Washington, their specifications were that hot water reach each fixture in under 30 seconds. At the time, I'd never thought about it. Now its a standard for all of my projects.

When you have a building where opening walls just isn't feasible, a pump that dumps hot water into the cold side is a reasonable compromise. Not ideal, but good enuf for the convenience of having on demand hot water.