Looking for help sizing water pipes.


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Old 10-28-09, 11:47 AM
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Looking for help sizing water pipes.

I have a 5 floor brownstone with Water Meter and 1” service entering building in Basement. There are 5 trunks off the this line; Basement, Boiler, Garden Apartment, Middle Riser and Rear Riser.

Basement - Services clothes washer, utility sink and 2 sill cocks. Recently replaced with ¾ copper. 11 WFSUs

Boiler - Services boiler with DHW coil. 6 gpm capacity.

Garden Apartment - Services 2 bathrooms with toilet, tub and vanity in each. Recently replaced with ¾ copper. 11 WFSUs

Middle Riser - Services 3 bathrooms on the third, fourth and fifth floors with toilet, tub and vanity in each. Services 1 kitchen on second floor with sink and dishwasher.
The Middle Riser is about 75 linear feet(50 vertical feet) from water meter to highest fixture(without elbows or other restrictions). Currently ¾” Galvanized on cold supply, 1” Galvanized on hot supply. 19.5 WFSUs.

Rear Riser – Services kitchens on the third, fourth and fifth floors with kitchen sink only in each.
Services a ½ bath on second floor with toilet and vanity.
The Rear Riser is about 105 linear feet(47 vertical feet) from water meter to highest fixture(without elbows or other restrictions). Currently ¾” Galvanized on cold supply, 1” Galvanized on hot supply. 8 WFSUs.

In addition to the Middle and Rear Risers, about 50 ft of galvanized pipe from the water meter to these these risers need replacement.

With a total WFSU of 49.5, 105 feet of pipe length and 50 psi incoming water pressure, the UPC pipe sizing charts indicates that supply lines should be 1 ¼.

A few questions..

1.Are my WFSU calculations correct?
2.Do the demand tables assume that hot water storage is being used? How does using a Boiler coil affect demand calculations?
3.Do I run 1 ¼ pipe all the way to the floor with the highest fixture, or reduce diameter as I go up in floors?
 
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Old 10-28-09, 11:21 PM
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I'm not sure if your calculations also are taking into account the pressure loss associated with vertical rise. Did you measure your 50 PSI number at the main service line coming in through the wall? For every 2.3 feet of rise you have, it will diminish your pressure by one PSI. On the "middle riser" you stated you had about 50 feet of vertical rise which means your 50 PSI will be reduced to 29 PSI by the time it climbs that high. This will drop you into the lower WFSU table so keep that in mind for both the middle riser and rear riser.

I would recommend pulling apart a galvanized joint or two to check the condition of it if you are planning on keeping it. It is not uncommon for old galvanized pipe to corrode badly and turn a 1" pipe into an effect .75" opening. If that's the case in your situation it will only restrict your flow even further.

You may want to price a booster pump vs. all new plumbing to see which is most cost effective. With as much plumbing as it sounds like you need to do, your money may be better spent on a booster pump to increase the pressure to maybe 75 PSI on the lines thus increasing the WFSU rating for each pipe diameter.
 
 

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