# Help me understand hot water supply vs. 2021 IPC charts

### Users who are viewing this thread

#### millsryno

##### New Member
I'm probably not understanding something correctly here, so please educate me. I've looked and looked and can't find the info.

I'm remodeling my house and trying my best to make sure I do everything right. So rather than just assume I need to loop a 3/4 hot water supply line off my 50 gallon electric water heater (has 3/4 input and output with recirc pump), I pulled up the 2021 IPC and calculated out my WSFU and cross referenced that to the distribution pipe size chart.

I calculate this water heater needs to supply 16.2 hot WSFU. This is from 3 bathroom groups (1.5 hot WSFU each, 4.5 total), laundry room (2 hot WSFU from washing machine and dog wash station that uses a shower hand wand), sink in a pantry (1 hot WSFU), kitchen (includes two sinks and two D/W- total 4.8 hot WSFU), powder room lavatory (0.5 hot WSFU), in-law suite kitchenette (includes sink and D/W - total 2.4 hot WSFU) and in-law washing machine (1 hot WSFU).

When I look at table E104.1 for water meters, mains and distribution piping size for 50-60 psi, am I supposed to reference the column for distribution pipe to determine what size line is needed for a trunk? I can't find a definition for distribution pipe and I am assuming it means the trunk line or in this case the hot water loop. Is this correct? There is one line on the table for 3/4" distribution pipe and it shows only 9.5 WSFU (max). Going by this chart I would need to upsize to 1" distribution pipe if I had 150' or less of developed length. I probably have about that.

With the water heater only having a 3/4" outlet, wouldn't that cause a bottleneck and essentially nullify the added ability of the 1" line to supply the hot water? Interestingly, my perception is that I only see 3/4" hot water trunk/loop lines being used in my area and then downsized to 1/2" to the fixtures. I must not be looking at this correctly. Please educate me.

#### millsryno

##### New Member
I'm probably not understanding something correctly here, so please educate me. I've looked and looked and can't find the info.

I'm remodeling my house and trying my best to make sure I do everything right. So rather than just assume I need to loop a 3/4 hot water supply line off my 50 gallon electric water heater (has 3/4 input and output with recirc pump), I pulled up the 2021 IPC and calculated out my WSFU and cross referenced that to the distribution pipe size chart.

I calculate this water heater needs to supply 16.2 hot WSFU. This is from 3 bathroom groups (1.5 hot WSFU each, 4.5 total), laundry room (2 hot WSFU from washing machine and dog wash station that uses a shower hand wand), sink in a pantry (1 hot WSFU), kitchen (includes two sinks and two D/W- total 4.8 hot WSFU), powder room lavatory (0.5 hot WSFU), in-law suite kitchenette (includes sink and D/W - total 2.4 hot WSFU) and in-law washing machine (1 hot WSFU).

When I look at table E104.1 for water meters, mains and distribution piping size for 50-60 psi, am I supposed to reference the column for distribution pipe to determine what size line is needed for a trunk? I can't find a definition for distribution pipe and I am assuming it means the trunk line or in this case the hot water loop. Is this correct? There is one line on the table for 3/4" distribution pipe and it shows only 9.5 WSFU (max). Going by this chart I would need to upsize to 1" distribution pipe if I had 150' or less of developed length. I probably have about that.

With the water heater only having a 3/4" outlet, wouldn't that cause a bottleneck and essentially nullify the added ability of the 1" line to supply the hot water? Interestingly, my perception is that I only see 3/4" hot water trunk/loop lines being used in my area and then downsized to 1/2" to the fixtures. I must not be looking at this correctly. Please educate me.
Can anybody enlighten me?

Replies
5
Views
366
Replies
11
Views
233
Replies
1
Views
178
Replies
0
Views
155
Replies
5
Views
220
Hey, wait a minute.

This is awkward, but...

It looks like you're using an ad blocker. We get it, but (1) terrylove.com can't live without ads, and (2) ad blockers can cause issues with videos and comments. If you'd like to support the site, please allow ads.