How to deal with 3/4" bathroom lines with homerun system

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Old 03-17-19, 03:01 PM
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How to deal with 3/4" bathroom lines with homerun system

Hi Everyone - it's been a while since I've posted and we've since moved into a new house. I don't post often because generally I can find what I need but this one has me scratching my head.

Both full baths have 3/4" lines branching off a 3/4" trunk from the basement. Every other fixture in the house has straight 1/2" running to it branching off the same 3/4" trunk. The fixtures in the bathrooms are reduced from 3/4" to 1/2". I want to install a PEX manifold in the basement as it's unfinished and have every opportunity to make things the way I want but I can't find manifolds that do 3/4" outlets. I've also never had water pressure issues with 1/2" lines running to the bathrooms since I'm pretty sure the flow is more than enough to support a shower, sink and toilet as long as it comes off a 3/4" trunk.

The question is this: would there be any issues running a 1/2" line from a manifold to a 3/4" line that runs up through the walls and gets reduced back down to 1/2" in the bathrooms. I wish it was just a straight shot up the walls because I could snake a 1/2" line up the 3/4" pipes but there's lots of turns going through walls and floors. I don't believe I'd see a pressure drop since I wouldn't be pulling more than a normal 1/2" line can provide, but I wasn't sure if up-sizing the diameter would reduce the overall pressure...it's been 10's of years since my last physics class...

If it helps, we're on a well system here that goes from 1" from the pressurized bladder, down to 3/4" to the filters and so on. The bladder is set to the default of like 25-40psi (kicks on when tank hits 25, off when it hits 40). I have a good bit of room to increase the pressure if necessary.
 
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Old 03-17-19, 06:00 PM
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1/2" (all the way) is sufficient to supply one fixture. That's why the manifolds are most commonly found with 1/2" outlets. One for each fixture. If you are doing a manifold system then run a 1/2" line from the manifold to each fixture.

NO, you can't put some 3/4" tubing in a 1/2" run and expect anything. That run is constrained by the 1/2" at the beginning and you should just consider it 1/2" the whole way even though there is 3/4 in the middle. You can use 3/4" but for the length of run in most houses you won't notice any benefit.

If you only want to run one line up to the bathroom then it sounds like a manifold system is not right for you. Just run 3/4" trunk lines and T off with 1/2" to each fixture.
 
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Old 03-17-19, 06:41 PM
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Thanks for the quick response! I was thinking as much but really needed a sanity check here. It seems a home run system is really on reasonable for a total remodel, or new construction with options considering the raw number of lines you have to run and the amount of walls you have to get your other half to let you cut into.

My supply does support 1", but obviously the hot water only supports 3/4" and I doubt I'd see a reasonable change increasing the cold volume. I think for now I'll just replace everything with new 3/4" PEX and remove old elbows with curved pipe to add anything I can to flow rate. Everything is 21 year old CPVC and within our first year here I've replaced several elbows and more than a handful of valves so I want to pull everything out of the basement now before I do any finishing.

The last thing I'd like to add is that when our laundry runs it's a noticeable drop in pressure in most of the house. That room gets a 1/2" supply off the main 3/4" trunk so I'm guessing when the washer fills it's just hot and cold wide open and it also happens to be the very first branch off the trunk. I wonder if shutting the valves half way on the shut-offs if it would help. I don't care if it takes 10 more minutes for the laundry to run.
 
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Old 03-18-19, 05:32 AM
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Closing the valves could help but it sounds like a supply problem. Probably most common are pressure switches that are 30/50 or 40/60 which would be a noticeable improvement over the pressure you have now. The question is whether or not your well pump can supply water fast enough to support that pressure while the washer is filling.
 
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Old 03-18-19, 11:08 AM
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I don't see any reason to run 3/4" to fixtures (unless you have a multi-head shower setup). Though the only time it really 'hurts' is when you're waiting for hot water.

The way I see it, you can either:
1) Leave the 3/4" as-is and just extend to your manifold with 1/2"
2) Run 3/4" to your manifold, and adapt it there to 1/2"
3) Run 3/4" to your manifold and build your own manifold using some 3/4" valves.

I'm not usually a huge fan of manifolds unless the house really lends itself to it. As long as you have valves where you need them, it's not like you're turning fixtures on and off daily. I find it adds cost (manifold + tubing) and doesn't really get you much.
 
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Old 03-18-19, 12:27 PM
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I agree with your sentiment about the manifold. My main selling point on it is access to the shut-offs after I put a ceiling up, though it'll be a drop ceiling plus all shut-offs require access panels anyway. I think between yours and Pilot Dane advice I know what I'll do. I will likely just keep everything the way it is by replacing the existing 3/4" cpvc and putting in 3/4" PEX but I will use more curves instead of elbows to maximize flow where possible and have someone come out to adjust the tank pressure and verify that the pump can keep up with a higher rate. I remember the well company said the pump we had was an entry level version and it likely wouldn't last long so I'm sure that'll be something we have to replace soon anyways.

Thanks to both of your for the advice and ideas! If anyone is wondering why I'm not using cpvc again, it's because I already have the parts and gear to do PEX and I like being able to curve it rather than have lots of elbows.
 
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Old 03-18-19, 12:37 PM
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Unless you have documentation on the pump the well company won't be able to tell you much about it without pulling the pump out of the well. Even then I wouldn't pay someone to come out for that. It will do what it can and knowing it's numbers won't change anything.

Many pressure switches can be adjusted to a certain amount. The instructions are usually on the plastic cover. If your switch can't be adjusted up to where you want then replacing the switch is the next option and luckily they are reasonably priced.
Then you need to change the air charge in your pressure tank (when the system is off and all water bled out) to be 2psi less than the pump's cut in (turn on) pressure.
 
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Old 03-18-19, 06:27 PM
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You are correct but fortunately we have the documentation on the pump that was replaced here a few years back. I'd have to dig it out of the depths of the filing cabinet to get more info. The tank does have the adjustable nut/springs on the pressure switch and I've seen how to adjust them. I also have the hose bib to drain the tank while testing the settings so that won't be an issue. I guess worst-case is we prematurely burn an entry level pump out from causing it to run more frequently. Next time around I'll have the ability to pick my own and in the grand scheme they aren't all that expensive.

I did check the air pressure on the tank and it's exactly where it needs to be. I honestly don't know why I keep thinking this is more complicated than it really is. I'm just new to well systems and even though I worked on swimming pool maintenance for a decade for a job I keep thinking this is some mystical water delivery system.
 
 

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