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Recirculation system question/idea

TAGTAG Posts: 200Member
edited December 2019 in Domestic Hot Water
While I was originally going to pipe my new project in copper -- the long delay combined with seeing a few PEX plumbing systems has changed my mind. Think the "home run" Viega system may be the way to go. I'm wondering if anyone has real world experience with max distance and hot water wait time.

The preferred location for both boiler and indirect puts them under the kitchen next to a full bath -- so nothing is very far away there. Simple Grohe thermo valve and head. No body sprays or bathtub in the house. The second bath is about 18' away so the shower valve will be some feet more pipe wise and the sink a few more still -- let's say 25 feet. I'm going to insist the pipe is insulated .... but I'm wondering if I should figure out some recirculation solution?

I could do another two place manifold in the bathroom or I guess simply run a single 3/4 PEX to the bath and split to the sink and the shower and do a typical dedicated 1/2 PEX return loop.

On my other systems I always use a Laing pump with internal thermostat -- separate time controller. Some people now use a an occupancy sensor --

There is a chance that my mechanical room may not be big enough for everything -- causing the DHW tank to move about 15' from the boiler. This only changes the distance to that same distant bathroom -- now much further. If I have to do that I don't think any question it needs recirculation -- over 40'

I'm surprised how little information is available for new system w/ dedicated lines .. and nothing about "home run" systems. It's all retrofit systems with the mixer using the cold .... don't want that.

Comments

  • hot_rodhot_rod Posts: 12,584Member
    Follow the Viega recommendation, I think 70' or less from manifold to fixture?

    I used that system back when Vanguard started it, be sure to not oversize the tube, 3/8 or 1/2. It's the small diameter, low volume that allows the lines to flush quickly and not need a recirc.

    On a tub filler you can go with a larger tube, it will be warm after a few gallons.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • TAGTAG Posts: 200Member
    Did you use any 3/8 ? Some say pressure drop occurs -- this project is on a well .. so it's 40-60

    My plan was typical 1/2 manifold ..... unless I do the one line with 3/4. Know the PEX has smaller diameter -- and the Viega fitting are smaller than Uponor
  • hot_rodhot_rod Posts: 12,584Member
    3/8 is used for lav sinks which are .35- .50 gpm typically, probably adequate for a kitchen sink also.

    They should have a chart showing distance, required flow rate and suggested tube size. This system has been around for probably 30 years now, a proven method. It's nice to have an accessible isolation valve for every run in the home.

    It is tube extensive, that is the trade-off. You leave the manifold location with a large gob of tube, typically zip tied into a bundle.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • TAGTAG Posts: 200Member
    hot-rod: The idea is great -- less fitting -- easy shutoffs. What I find amazing: The lack of feedback from actual users.

    Yes it can make a bit of a mess at the manifolds ... the manufacturers should really design some sweeps or "something" into them.

    3/8 is obviously fine for an ice maker -- and, if you look at most sink faucets the feeds are all small tubing. But -- what's real world with 3/8 tubing with various sink faucets in a typical house.

    It's like HVAC zoning. I grew up in a house with it -- have put it in every house I have built (except one that I regret). With new multisided systems --it's even better. But: All too many professionals still will shy away. My contractor has more than one plumber for quotes ... but -- With the first I got "when we do it we always use 1/2" and they have never done any recirculation.

  • hot_rodhot_rod Posts: 12,584Member
    here is the pressure drop chart for Uponor 3/8 pex, 100 foot length.

    .5 gpm flow at 120° about 1.3 psi drop. So if you stay within the 70' recommendation I doubt you would even notice the pressure drop.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • Larry WeingartenLarry Weingarten Posts: 1,677Member
    Hello, One more thing you can do to cut waiting time is to move the manifold to directly on top of your water heater. I made my own copper one and ran 3/8" PEX from it. I think the worst wait is 15 seconds, and the best is the kitchen sink at about four seconds. :)

    Yours, Larry
  • TAGTAG Posts: 200Member
    So you have found no problems with the 3/8 tubing .... ?

    Also -- what type PEX?


    My manifold will be very close to the tank regardless of it's location
  • hot_rodhot_rod Posts: 12,584Member
    TAG said:

    So you have found no problems with the 3/8 tubing .... ?

    Also -- what type PEX?


    My manifold will be very close to the tank regardless of it's location


    Both my house and shop are piped with home run 3/8.

    I ran 1/2 to the tub filler and two hose bibs are also 1/2. It works just fine as long as you have adequate pressure. My well pressure runs 40/60lbs. it rare to fund any water system less than 30 psi.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • TAGTAG Posts: 200Member
    edited December 2019
    Thanks hot_rod .. I did not get from your earlier comments that you installed and lived with it. Maybe did it for a job .. not personal space.
  • Larry WeingartenLarry Weingarten Posts: 1,677Member
    Hello @TAG , I used Wirsbo/Uponor for my PEX. There is little flow restriction at fittings with this system. Much like @hot_rod did, I used 1/2" for hose bibbs with 3/8" for the rest. I have 60 psi and it works fine. I did find that using 1.5 gpm showerheads gives a more forceful shower. By putting the insulated manifold directly on top of the heater, it stays full of hot water, so when I have a draw, only the 3/8" tube needs to be flushed. That really speeds up hot water delivery.

    Yours, Larry
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