does this sizing sound right?

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Barrybpdx

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i'm replacing the 1926 galvanized pipes and i'd like to feel confident about the pipe sizing i'm planning. my goal is to have adequate supply (of course) but not waste too much hot water waiting.
- my "fixture units" count is 30 on 3 levels
- i think the city is giving me around 40 psi
- i've got 3/4" galvanized from meter to house (which i'm planning to replace with 1" copper soon but not now)
- once in the house, i'm running 1" copper to the HWH and to where the cold starts branching
- 3/4" copper from HWH and serving all branches
- 1/2" copper on branches which are grouped like this:
- tub/shower w/ remote pressure balance
- shower, toilet
- toilet, hose bib
- 2 lavs

currently everything inside the house is 1/2" galvanized except for 3/4" to the HWH and to the first branch and this gives us acceptable flow.

as for not wasting so much hot water, i'm thinking of a tankless heater in the attic above the upstairs bathroom which is where 80% of the waste occurs.
our 50 gal HWH is plenty big for us, but those recirculating systems still waste energy on re-heating the water even if the water itself is conserved.
 
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Cass

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Instead of copper you may want to consider running plastic. At least from the W/H to the fixtures. It will draw much less heat than the copper, and you may not need the tankless ( I don't like them) by doing so.

Sizing sounds good, water pressure is low, call the city/town and find out what the pressure is or buy a pressure gauge and check..
 

hj

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plastic

If you go with plastic, you want to realize that the internal bore is smaller than the equivalent copper size, so you might want to reduce the amount of 1/2" you use.
 

Bob NH

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Check Out Point-of-Use

A small point-of-use heater like the Ariston GL2.5 costs about $140 and solves the problem of not having hot water at the end of the line. The point-of-use heater goes in the hot water line at the destination, and requires only a 115 Volt circuit for power.

It saves the cost and aggravation of the instant heater and doesn't waste heat like the circulating systems. You will use about 0.6 gallon before the hot water from your main heater arrives so the temperature will not be significantly affected.

If you do the cost/efficiency analysis yourself, you will probably come to the conclusion that point-of-use gives you everything you need at the lowest cost.
 
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