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tankless water heater and water pressure pump reccomendations

Posted by giuseppe_paolo (My Page) on
Mon, Apr 18, 11 at 0:57

I am planning to have the tankless and the water pressure pump just to feed the master bathroom because of the Kohler dtv (8 body sprays and 2 shower heads with a third not on the digital valve will eat up hot water and pressure) most likely unless it is deemed easier or beneficial to have it feed the whole house but really only needed for the master bath.

Also a corner air bath which will need good volume and pressure to fill and enough hot water to fill it without running out possibly back to back with the shower.

I am leaning towards a Takagi tankless water heater but which one?

The T-K3 or the T-H2?
http://www.takagi.com/index.php?p=products.php&page_id=2&category_id=1
The T-H2 gives more gpm so thats probably the one to go with between those 2 Takagi models.

or maybe twin Rinnai R75LSi units? I may likely need 2 but would obviously prefer a tankless (whichever brand) of size and capability in which 1 would be enough for just the master bathroom

as for the pressure pump,
What do you guys think of the Pentair Water 3075SS Pressure Water Booster System 3/4 HP 115-Volt

seems like what I need and has some good reviews on Amazon and the like.

again this, like the tankless, would ideally feed just the master bath.

I will have my plumber/contractor look at our water and gas lines to determine what type we need and start planning placement/install but before even looking he was confident he have both feed just the master bath and at least with the tankless was even what he suggested from the start.


Follow-Up Postings:

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RE: tankless water heater and water pressure pump reccomendations

I suspect that, like me, most other folks reading this post just kind of sit there with their jaws dropped and mouths open afterward.

I know there are people out there who do this sort of thing, but it's a different neighborhood than the one I live in.

If you're spending say $6k on just the equipment to feed hot water to your 15 gallon per minute shower system in the one bathroom, you likely have enough $$ to hire a professional (plumber, maybe even a registered P.E.) to design it for you.

Congratulations, name sounds Italian but you've definitely arrived as a prototypical, wasteful American.

Here is a link that might be useful: Fine Homebuilding: Living better but wasting less


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RE: tankless water heater and water pressure pump reccomendations

Yeah thull, I'm with you...

Wonder if his water is even metered.


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RE: tankless water heater and water pressure pump reccomendations

first of all, yes there are lots of ppl even on the forums that do showes with body sprays. I got them all for very reasonable price. I wasn't planning on doing any sprays but my wife requested and after initially said no, I gave in and found some. figured you can't just get 2 (though actually that would have been good) so I got 4. then I realized I needed rough in valve and trim to control them and thats how I discoverd the kohler digital valve that controls everything from one valve and a control panel so saving me from getting a bunch of diff roughs and trims.

I got the DTV and interface online and ebay relatively inexpensive. and through the Kohler DTV I saw its often used with the kohler water tiles which I liked better then the off wall sprays I had already got and were un returnable so I got 4 of the water tiles also for a great price.

As you know on the bathroom forums, everyone goes over budget and does more then they planned on as was the case here with one thing leading to another.

Also, the interface controling the digital valve will allow us to lower the water pressure and we wont be using all sprays at once so it is not going to be a big water waster.

didn't spend 6k on equipment and tankless wont be even half that. water is metered. will only use it once a week myself and wife will use everyday with just one shower head and maybe 2 body spray.

Thanks for your post.... I think, though you seemed to just criticize, jump conclusions and help none.


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RE: tankless water heater and water pressure pump reccomendations

If you're bargain-hunting for fixtures and DIYing things, I get it. There are things in my house I'd never have if I'd had to pay someone else for a soup-to-nuts install job.

That said, what you want to do is hugely expensive to put in and wasteful in operation. I stand by my guesstimate that you're spending $6k on water heating equipment for your uber shower.

If you put in 2, each tankless unit (installed by a pro) will cost around $2k. That's including piping them up and running the stainless exhaust pipe outside. Firing those 2 burners at 180k to 200k BTU/hr likely will require upgrading your gas line, which could also easily be $1.5k plus.

If you put in 2 showerheads and 8 sprays, that's around 25gpm of flow you need to provide. If the water piping in the home isn't big enough to provide that much flow, adding a booster pump ($600 to $800 installed) won't help. If it can't pull the flow required from the suction side, it will cavitate and you'll just destroy your $300 pump in short order. You'll need to have enough supply based on code for potential other simultaneous uses. Also, what's going to turn it on/off? It can't just sit there running when there's no flow downstream (i.e. nowhere to pump to). Thus the need to hire a professional if you really want to do this.

You will also need to make sure that your drain piping can handle 25gpm. Again, there's a code calculation method to determine this.

In operation, shower plus 2 sprays is ~7.5 gpm. That costs ballpark of $3/hr for gas (37F delta T, 90% efficient, $1/therm). It goes up to $10/hr to run flat out at 25 gpm (and I'm not sure even 2 tankless heaters put out that much heat).

That's the quick-and-dirty, likely mistake-laden assessment of some of the issues of what you want to do. In more places than you'd think, water is a scarce, expensive resource that we don't really pay the real costs of producing. If everyone and their brother pulled out their flow restrictors or put in something like this, we'd be in big trouble.


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RE: tankless water heater and water pressure pump reccomendations

If you're bargain-hunting for fixtures and DIYing things, I get it. There are things in my house I'd never have if I'd had to pay someone else for a soup-to-nuts install job.

That said, what you want to do is hugely expensive to put in and wasteful in operation. I stand by my guesstimate that you're spending $6k on water heating equipment for your uber shower.

If you put in 2, each tankless unit (installed by a pro) will cost around $2k. That's including piping them up and running the stainless exhaust pipe outside. Firing those 2 burners at 180k to 200k BTU/hr likely will require upgrading your gas line, which could also easily be $1.5k plus.

If you put in 2 showerheads and 8 sprays, that's around 25gpm of flow you need to provide. If the water piping in the home isn't big enough to provide that much flow, adding a booster pump ($600 to $800 installed) won't help. If it can't pull the flow required from the suction side, it will cavitate and you'll just destroy your $300 pump in short order. You'll need to have enough supply based on code for potential other simultaneous uses. Also, what's going to turn it on/off? It can't just sit there running when there's no flow downstream (i.e. nowhere to pump to). Thus the need to hire a professional if you really want to do this.

You will also need to make sure that your drain piping can handle 25gpm. Again, there's a code calculation method to determine this.

In operation, shower plus 2 sprays is ~7.5 gpm. That costs ballpark of $3/hr for gas (37F delta T, 90% efficient, $1/therm). It goes up to $10/hr to run flat out at 25 gpm (and I'm not sure even 2 tankless heaters put out that much heat).

That's the quick-and-dirty, likely mistake-laden assessment of some of the issues of what you want to do. In more places than you'd think, water is a scarce, expensive resource that we don't really pay the real costs of producing. If everyone and their brother pulled out their flow restrictors or put in something like this, we'd be in big trouble.


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RE: tankless water heater and water pressure pump reccomendations

I am no expert in this area but I do have some body sprays and a pump in my house. I know nothing of the tankless heaters.

Anyway, I have a Davey system (looks just like the Pentair). I had trouble with low pressure but it sounds like you're confusing your need for volume with your need for pressure. Assuming your pressure is good then what you need is larger supply plumbing. You'll need to calculate the GPM of all the fixtures you plan to have running at once, then size the supply piping accordingly. You can only force so much water through a small pipe before you start creating velocity issues (ie water hammer). So assuming each ficture has a 1.5gpm limit you'll need to supply 15gpm just for those 10 fixtures in the shower. Thats a lot of water and I'd 'guess' you'd need at least 1.5" supply. Furthermore the pump you want to buy can't boost the pressure for that much volume. Again, if your pressure is good its pointless. Lastly don't forget if you need a 1.5" supply for the shower it needs to be at least that size from your water source. So if you only have 3/4" plumbing coming in you need to reevaluate.

Hope this helps some.

Joe


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