Avoiding Pressure Loss

Post by **Richard S.** » Tue. Oct. 15, 2019 12:31 am

One of my first projects at the old/new house is to replace most of the copper. A lot of it is really old as in 60 or 70 years and I want to separate it so each unit has it's own supplies. The giant jumble of tubing going everywhere some of which doesn;t even make sense is another inducement. One of the main reasons I'm doing this is so can meter it myself and pass the cost onto the tenants.

The water main is one side of the house and the water heater is on the other side. From the main I can either run a line direct to the hot water heater OR first supply the cold water and run that to the water heater and then loop it back. I'm wondering if going with the first option would help with pressure drops? I realize the pressure is what it is but that should help with volume availability?

This is double block and I'm converting two larger rooms that are separate for myself, so it will be three households. My other thought was using two pressure reducing valves, one for the cold and the other for the hot. This would give me street pressure before the split.

Everything is going to be 3/4 except the supplies branching off to individual fixtures.

Any of this make a difference or just loop it back?

CapeCoaler · Post by **CapeCoaler** » Tue. Oct. 15, 2019 11:06 am

If you run direct to the DWH you bypass the concept of metering...
You will need 3 DWH...
Do a 1" loop around the perimeter of the basement...
Put in 3/4" tees for each unit plus a few more for future use...
Put ball valves on the 3/4" tees...
Just a primary/secondary setup...
From there you can drop down a meter any where...
All drops will have equal pressure from the loop...
Then you can run irrigation if needed...
Or have common water for car washing...
Any other common use like laundry?...

Post by **Richard S.** » Tue. Oct. 15, 2019 3:37 pm

CapeCoaler wrote: ↑
Tue. Oct. 15, 2019 11:06 am
If you run direct to the DWH you bypass the concept of metering...

The supply for upstairs and the downstairs sinks are all right in one area for both sides of the house so I don't have to run a lot of pipe off main line. There is three units so each unit will have meter for both the hot and cold, six altogether. I don't see anyway of avoiding that unless I want to install hot water heaters for each unit.

Do a 1" loop around the perimeter of the basement...

Should of mentioned this, the supply from the street is only three quarter..... otherwise I wouldn't even be asking.

Sunny Boy · Post by **Sunny Boy** » Tue. Oct. 15, 2019 4:22 pm

When I was studying architectural drafting in college, the idea was to "feed" the water system like our spinal column and ribs branching off it, or branches of a tree. When the water meter is 1 inch, use 3/4 inch branches off the 1 inch to split off to all the 1/2 inch copper that branches off the 3/4 inch and all runs should be as short as possible. If you measure the cross section of each the step up in size has quite a lot more flow capacity.

When I redid the cobbled-up old mix of plumbing in my old house, I ran a 1 inch copper feed line from the water meter right down the center of the house's basement (the spinal column). Working with the shortest distances off that 1 inch line to what needed water feed, I branched off to sinks, bathrooms, washing machine, dish washer and garden hose.

The result was, no matter what appliance was using water,- including back yard sprinkler - no more screams of too hot or too cold from whoever was in the shower.

Figure out where you need the water and run your biggest feed line between those points to keep the branches (and flow resistance) as little as possible.

Paul

Post by **Rob R.** » Tue. Oct. 15, 2019 4:52 pm

Large diameter piping prevents noticable pressure drop when multiple fixtures are used, but it also requires purging more water at the tap before it gets hot.

I would transition to 1" right after the pressure reducing valve, and run that to the water heater. Run 3/4" branches off that "trunk line" to supply cold water to each unit, and after the water heater I would run 3/4" to each unit. A "home run" pex manifold for each unit would work slick.

Sunny Boy · Post by **Sunny Boy** » Tue. Oct. 15, 2019 5:35 pm

Rob R. wrote: ↑
Tue. Oct. 15, 2019 4:52 pm
Large diameter piping prevents noticable pressure drop when multiple fixtures are used, but it also requires purging more water at the tap before it gets hot.

I would transition to 1" right after the pressure reducing valve, and run that to the water heater. Run 3/4" branches off that "trunk line" to supply cold water to each unit, and after the water heater I would run 3/4" to each unit. A "home run" pex manifold for each unit would work slick.

If your having to purge a lot of cold water to get hot water then it's positioned and plumbed wrong.

None of the branches using the larger diameter needs to be purged, since the feed from the water heater, if it's properly centrally locate, is the smaller lines. The water heater gets fed with a larger line, but branches off to feed with 1/2 inch.

If the water heater is stuck off away from where being centrally where it's needed then it needs to be moved, or live with the results of that.

The point of my classes was to design the system to avoid having problems that need to be compensated for in other ways.

It can be done and in my pre-1900, 4000+ sq foot, very long, old Victorian house, I've done it, by following the examples I mentioned.

Paul

Post by **Rob R.** » Tue. Oct. 15, 2019 6:58 pm

Paul, that makes sense - I was not trying to contradict you.

I am a big fan of small diameter pex run to each fixture. My brother did that in his home and the performance is outstanding.

Sunny Boy · Post by **Sunny Boy** » Tue. Oct. 15, 2019 7:46 pm

S'ok Rob.

Having lived with five females - wife and four teenaged daughters - and then had to redo the plumbing after pipes froze during a power outage, I was "inspired" to remember those classes about how to make the plumbing help my life be easier,.... meaning,.... hearing less complaints !

Paul

Post by **Richard S.** » Tue. Oct. 15, 2019 8:39 pm

Sunny Boy wrote: ↑
Tue. Oct. 15, 2019 4:22 pm
When I was studying architectural drafting in college, the idea was to "feed" the water system like our spinal column and ribs branching off it, or branches of a tree. When the water meter is 1 inch, use 3/4 inch branches off the 1 inch to split off to all the 1/2 inch copper that branches off the 3/4 inch and all runs should be as short as possible. If you measure the cross section of each the step up in size has quite a lot more flow capacity.

My problem is I'm starting off with 3/4 coming through the wall so running anything but 3/4 is a bit pointless AFAIK. In any event it's done deal at this point. I'm splitting it at start before any fixtures. If I have any issues I'm assuming running street pressure to individual pressure reducing valves should help if I need to do that.

Post by **Rob R.** » Tue. Oct. 15, 2019 8:43 pm

What is the street pressure?

Post by **Richard S.** » Tue. Oct. 15, 2019 8:46 pm

Rob R. wrote: ↑
Tue. Oct. 15, 2019 8:43 pm
What is the street pressure?

I haven't checked Rob but it's pretty high. BRB.

CapeCoaler · Post by **CapeCoaler** » Tue. Oct. 15, 2019 8:58 pm

We had 75 psi at the old house by the beach...
Lowest point in the water system...
Current house has 45 psi...
one of the higher points in the same town...
Thinking of putting in a pressure booster...
Because during high draw downs during the summer months...
Pressure drops to about 35 psi on the second floor...

Post by **Richard S.** » Tue. Oct. 15, 2019 8:58 pm

Nevermind, don't have the right reducing fitting. I'll get one tomorrow to test it, old plumbing is still in place and there is drain before the old pressure reducer I can test it on. That was for outside hose, it exploded more than a few of them. LOL

Post by **Lightning** » Wed. Oct. 16, 2019 7:50 am

Richard S. wrote: ↑
Tue. Oct. 15, 2019 8:39 pm
My problem is I'm starting off with 3/4 coming through the wall so running anything but 3/4 is a bit pointless AFAIK.

I don't know if that is totally accurate. Seems like stepping it up to 1 inch would cut down on friction loss.. IF friction would be a factor, I don't know.

Post by **Richard S.** » Wed. Oct. 16, 2019 2:46 pm

Rob R. wrote: ↑
Tue. Oct. 15, 2019 8:43 pm
What is the street pressure?

It's only 115 psi. LOL