Water supply and distribution plans - Seattle home

[DavidTu]

I'm going to be putting up a few inquiries seeking help in designing and sizing our pipe layout for the water supply. Rather than spin off a lot of little questions in a lot of threads, I am hoping I can concentrate all the supply questions here so please check back as additional questions will be posted here.

This is a seattle-area home that is about 3500 sqft. There's a basement, main and second floors. The following fixtures will be present:

Basement - a) bath cluster with tub/shower combo, toilet, lavatory; b) laundry cluster with washer and double laundry sink just outside bathroom; c) hot water tank(s) {bath and laundry clusters are adjacent}

Main - a) powder room cluster with toilet, lavatory; b) kitchen cluster with kitchen sink, small island sink, dishwasher, refrigerator (icemaker)

Second - a) master bath cluster with standalone shower, bathtub, toilet, 2 lavatories; b) other bath cluster with tub/shower combo, toilet, 2 lavatories; c) laundry cluster with washer and laundry sink {all three clusters are adjacent}

Water supply is 1" PE from the meter.

** NEW:1/28/12 Please see supply isometric diagram attached **

 

[DavidTu]

Question 1 - do we need pressure reducing valve?

The city says that there's 96 psi at the meter. I measured 90 psi today at a sink spigot in the basement. Do we need therefore to install a pressure reducing valve to get the pressure to around 80 psi or below? Do the valves have a fixed pressure they regulate to or is it settable?

 

[Sponsor]

 

[Winslow]

You need a pressure reducing valve above 80 psi (UPC). Set it at between 50-60 psi.

 

[Gary Swart]

You will also need a thermal expansion tank set to the same pressure as the PRV.

 

[hj]

You should have a PRV and expansion tank. The only way to design a water distribution system is to have the blueprint or house available. Just knowing how many fixtures there are in each "cluster" is not enough.

 

[Jimbo]

Does this house already exist? Why is it being repiped? What size supply do you have from the street. Bases on all your usage, you certainly need a 1" supply. If you don't have that, you will be fighting pressure drops.\\\



96 psi is way to high to have in the house. 80 psi is MAX, and "normal" pressure is more like 60 psi.

 

[Terry]

You would work backwards from each fixture and size back to the main.

This chart is based on UPC
Typically, no more then two fixtues on 1/2". So a bathroom set with tub would be 3/4" on the cold and 1/2" on the hot.
Water pipe sizing

A 3 bath home in Seattle would be at least 1" from the main.

 

[DavidTu]

RE: Question 1 - PRV

Thanks everyone for your replies. Why is the expansion tank necessary? I've been told elsewhere that in Seattle we do not generally need expansion tanks so is this suggestion due to the PRV?

I may have use of an expansion tank elsewhere in the system, at least for hot water side. Does it matter precisely where in the system the expansion tank is located or would one near the water tank suffice? Or does it need to be in close proximity to the PRV and if so can you tell me or point me to info online about how that is installed relative to the PRV (before or after, etc)?

The water supply line is 1" PE from the meter.

 

[DavidTu]

Question 2 - what size water tank(s)?

Right now there is only a 50 gal tank, in good condition. I am certain we need more than that. Would the recommendation be to add an additional tank in series (and what size and which first?) or to replace the one tank with another?

The tank(s) would be located in the basement, below the two 2nd floor baths and near the kitchen.

On-demand water is not an option.

** No responses to this question yet is that because it needs to be posted in the water heater section? **

 

[DavidTu]

Question 3 - Supply branch pipe sizing

Please see the newly attached supply isometric on the first post of this thread.

We've done our best to give all the info you need to help evaluate our plans but let us know if we need to provide additional information. On the diagram we've gone ahead and put what we think are the correct pipe sizes for the various branches. Please let us know what we need to change.

There are a couple of things we are wondering right-off about where to run 1" PEX. Particularly should we run 1" PEX as we indicated in the diagram for segments CF and/or CD? Same question for segments be and/or bc. Also does it make any sense to run segment gab in 1" PEX as I believe water heaters have 3/4" input and outputs anyway (or can we get 1" attachements? and should we?).

In addition, we are wondering if the hose bibb that comes off the kitchen supply should be 3/4" or 1/2"? If we assume someone is going to attach a 100ft hose to the bibb do we
then want to upsize that line? (Probably it depends also on whether y'all will suggest that CD be 3/4" or not?)

Please note that the "master shower 1 & 2" are simply two shower heads in the same shower, but it is a standalone shower and one will likely be a rainhead.

Thanks for your help!

 

[DavidTu]

RE: Question 3 - Supply branch pipe sizing

Been revisiting the calcs... in Seattle the water meter is at the street. It is 3/4 pipe 6' and then a union to my 1" PE. If I take the measurement from the beginning of the PE, then I have 37' to the house, and 61' inside for a total of 98' max developed length. Given that I will use a PRV to lower pressure to 80 psi at the house's main it puts me in the 3rd table for sizing pipe, and the 4th column within that, correct? The build cwfsu total is 48 and the hwfsu at the water heater is 30. This gives me a 1" service and a 1" main for cold water. The 30 hwfsu gives me a 1" main for hot water (but doesn't water heater only have 3/4" fittings?). So segments AB and BC are 1", segments ga and ab are also 1".

Working back from point E we have 4 cwfsu, which could be handled by 1/2" , same for point d on the hot side with 4 hwfsu. Should we upsize to 3/4" anyway or are we good at 1/2" for the 2 lavs and tub/shower? My concern is that these segments DE and cd are essentially serial after the kitchen. Looking at point D with 9 cwfsu and point c with 6 hwfsu gives totals for segments CD of 13 cwfsu and bc with 10 hwfsu both can be handled by 3/4".

Working back from points G & f, we have 6 cwfsu and 6 hwfsu, respectively. Both could be handled by 1/2" except there's more than 3 fixtures so we upsize both to 3/4". Working back from point F there are 12 cwfsu for point F plus 6 cwfsu from point G for a total of 18 cwfsu on segment CF. Point e has 6 hwfsu plus 6 hwfsu from point f, for totals of 18 cwfsu and 12 hwfsu on the CF and be segments, respectively. Both can be handled by 3/4". The numbers seem to work for these segments being 3/4", however I'm a little nervous as there are 2 shower heads, a clothes washer and a tub plus two WCs all on this segment (ultimately) so any reason to upsize to 1" or are we good for 3/4"?

Working back from points H and h we have 14 cwfsu and 8 hwfsu, respectively. Both are handled by 3/4".

Working back through segment AB when we add in the water heater we get a total of 61 cwfsu, but that would require 1.25" main. Since it is bigger than the service line of 1" we do NOT upsize to 1.25" and stick with 1" main throughout ABC segment.

Question summary:
1) I'm inclined to upsize DE and cd from 1/2" to 3/4" unless there is a resounding "no you're wasting your money"... what say y'all?
2) Should we upsize any of CF, be, CD, or bc from 3/4" to 1"? Or are we OK using the calc results (3/4") as discussed above?
3) Can we get 1" connectors on the water heater or do we just drop 3/4" flex lines from the 1" hot water main?
4) Should the hose bibbs should be 1/2" or 3/4" runs? In one book it says they have to be 3/4" but I've seen Terry say he's used 1/2" so I presume that UPC does not require 3/4"? Is it recommended or not?

Thanks

For your convenience, I'm attaching a new updated version of the isometric here.

 

[DavidTu]

No Love?

Was hoping to get some input from any of the pros on our plans. We need to move forward so I'm just bumping this to see if we can get some advice before we do. It's either looking so good no one thought we needed the help or so bad they thought it hopeless

 

[Hackney plumbing]

Dont over size the hot lines or it will take alot longer to evacuate the cold from the hot line when calling for hot water at a fixture.

 

[Terry]

It's the weekend.
Way too much thinking for Sunday.
And Saturday was too nice for skiing in the mountains.

 

[DavidTu]

It's the weekend.
Way too much thinking for Sunday.
And Saturday was too nice for skiing in the mountains.

Fair enough. But, what's this "weekend" thing of which you speak?

 

[DavidTu]

So if we leave the 3/4" as-is are we good? Any other issues?