View Full Version : Pex Manifold ???'s
12-17-2008, 01:57 PM
Hi, new to this forum and I apologize in advance if these questions have been answered in the past, I tried to do a search ahead, but didn't come with any conclusions.
We are currently in process of buying an unfinished house. Unfortunately, all the plumbing needs to be done. The previous owner payed no attention to plumbing codes or even plain common sense in some areas. Our plan is to install the new system using pex, due to simplicity and cost.
I've read alot about remote manifold systems and central manifold systems and then home run systems. On some sites, I've read that you do not want to mix manifolds with control valves (meaning if I have a manifold with a dedicated line to my kitchen sink, I shouldn't also have a cut-off valve under the sink in addition to the manifold). Is this correct?? Doesn't seem to make sense to me why not.
My other question maybe more a matter of opinion. Do you find it better to have one central large manifold with dedicated lines to every ficture, or a smaller manifold with lines to different areas? Once you're in these different areas, such as the bathroom, then branch out to your fixtures, i.e. toilet/shower/sink.
Sorry about the newbie questions, but I just can't afford a plumber right now.
12-17-2008, 05:32 PM
The one big manifold in the basement with individual lines to each fixture is called a homerun system.
In a small home I usually just size the tubing correctly and run it in a conventional manner. I'm no fan of home run systems. It is impossible to recirculate hot water on a home run system and I hate waiting for hot water.
On a larger home I tend to go a bit hybrid. I pipe in the conventional manner then on a bathroom group I go with a mini manifold mounted in a closet or other access point.
12-17-2008, 05:40 PM
So with your hybrid, would you run 3/4 pipe to the bathroom and then attach a manifold with 1/2 pipe to your fixtures?? How then would you connect all your 3/4 pipe to your water supply without a massive amount of tees?? Is there a such thing as a manifold with 3/4 outlets??
Sorry for the many questions, if you know a good guide or book that I can learn more from, I'd be interested.
12-17-2008, 06:37 PM
Take a look at this link.
PEX Design Guide (http://www.huduser.org/Publications/PDF/pex_design_guide.pdf)
Take a look at page 28 and 30
I usually go heavily toward the system on Page 28 but incorporate the remote manifolds on page 30.
There are also flow through manifolds.
I like to have a definite end where a recirculation line goes back to the water heater.
12-17-2008, 06:52 PM
Yeah, I just found that guide, thank you. Really good info. I guess you would have a lot of tee's and such, but I guess most systems do. Also, your method seems to use a lot less redundant runs of pex. I was trying to figure out how to get five 1/2" runs of pex to my bathroom with out having to bore out 3" holes into my floor joists. Any good ideas for placement of these manifolds???
12-17-2008, 08:02 PM
Closets with access panels are good places for manifolds.
01-09-2009, 01:52 AM
This post was really helpful! The link to the Pex guide you posted is really helpful, big time.
I'm in the process of moving the washer and dryer to the second floor from the basement. The plumber who's working with me on this has already run the drain and he used red and blue pex for the supply lines.
The rest of this 60 year old house is about 70% copper and there's galvanized pipe in the basement that eventually will have to go. Per my plumber, he says he likes pex because once you learn it you can do a whole new house many times faster than anything else since pex can bend and flex so well. He told me it's supposed to last much longer than copper too, and that copper is just too expensive to use anymore unless he has to. He said he's still learning pex at this point and starting to get competant with it.
Now the questions:
Where the washer and dryer are going to be on the 2nd floor, the supply lines have to run through a first floor closet on an outside wall. I'm planning to insulate the closet the best way that I can, but does anyone know or have an opinion if pex would be more or less likely to burst if it starts to freeze? I know most plastics get more brittle when they are cold. I would think you professional plumbers try to avoid pipes close to outside walls in cold climates when you can, but if the closet is well insulated do you think this setup will be okay?
I would also really appreciate it if you could tell me a little more about how you recirculate hot water to keep it available hot at all times. It would be great if you could direct me to a good book or websites to read about it. I nevber heard of such a thing. I want to eventually get a tankless on demand hot water heater (I think), but I never heard of keeping the water in the lines hot before.
Lastly, if it turns out to be a problem from time to time, I was trying to figure out if there are any good shutoff valves out there that are either made for pex or can be adapted with adapters to the pex. I know there's electrically controlled valves out there that you could use to turn the water on and off from upstairs with the valves in the basement to protect against leaks. I've heard stories about how messy it gets when these upstairs laundry rooms spring a leak... (LOL)
01-09-2009, 06:42 AM
Pex stretches, so it is much less likely to burst than other pipes. The connectors, though can still burst. In the closet, leave the pipes on the room side of the insulation, or they'll likely freeze. Hot water recirulation basically uses a pump and a return line to move water from the water heater through the furthest fixture's supply, back to the water heater. There's a check valve and sometimes an aquastat that cycles things. Insulating your pipes is essential. If you don't have a dedicated return line, you can use the cold water supply line, but then your cold water will likely be warm until you purge it. If you use the cold water as the return, you need a valve to connect the hot and cold together when the flow needs to occur, and close when not so you can get cold. A bunch of companies make kits with all the bits you need. You can set it up to run on a timer, an occupancy sensor, on demand, or continuously. I have one made by RediTemp set to run on a timer for a bit in the morning, evening, and most of the weekend. Others are less expensive and can work well, too. If you are going to repipe, run a dedicated return line. You could always cap it off if you don't install a recirculation system, but it's harder to add after the fact.
Recirculation systems are required in many commercial situations, otherwise, you might have to run the tap for many minutes to purge the cold water and bring it to your tap - the heater could be many floors away.
01-09-2009, 03:22 PM
I still like copper. Prices of raw copper have plumetted. That means the prices for fittings and pipe should do too at some point. :)
01-09-2009, 07:12 PM
Thanks guys!!! I once put in a whole hot water baseboard system when I was 14, at the direction of the homeowner. He agreed to teach and feed me in exchange for work. In the end, he thought feeding me might not have been so great because I ate a lot back then. LOL
I've always liked copper a lot myself too. Solder the joints right and it will last with little maintenance for many years and its very sturdy.
Thanks especially Jadnashua. You seem to know plumbing like I know home control / home automation systems. I've installed five Omni systems by Home Auto Inc. ( www.homeauto.com ) so I know a lot about how to control things electrically / electronically. I don't know plumbing nearly as well.
Tell me, I was looking at the pex manifold pics you posted that go straight through with an in and an out. Was recirculation commonly done with traditional piping like copper, or is it more something thats come about with the pex since its so easy to run the additional needed lines?
I was thinking of converting my whole house to pex or most of it because it's a simple row house three floors 18 x 30. The only supply lines that go to the second floor are the two for the one bathroom in the house and now the pex to the washer. Eventually I would love to put at least 1/2 bath somewhere on the 1st floor, and I think a pex setup would help that to happen. This plumber I've been using is learning the pex real well at this point, maybe he would like to take out the old stuff and install pex.
Thank you both for the thoughts on the pex with cold exposure. I will make sure to insulate correctly and protect extra at the connectors! Still would like to find out more about eletrically controlled valves being available.
01-09-2009, 08:07 PM
Insulate as much as you want, but keep the pex (or any pipe) close to the inside wall, on the house side of the insulation.
Recirculation has been used in commercial situations for a very long time. Think about a hotel with a central water heater, and maybe 2-3" or larger pipes. Now, in the morning, how long do you think it would take to get hot water at the furthest point? Way after the customer had complained a lot. Back when a house had one bathroom, often right next to the kitchen, there was a short run to each, and it wasn't a problem. Now, with Mac Mansions and bathrooms spread all over the place, recirculation becomes not necessarily a convenience, but a significant water savings device as well. At least 5-6 companies make kits.
I get the impression that you are misunderstanding the manifold system. Once the water gets to the manifold the only place the lines go from there is to the faucet. There are no 3/4" tees, or any other tees for that matter in that line. Recirculation was done LONG before any one even thought of PEX. With a manifold system, the common way to recirculate is to do it to the manifold and then the user has to drain the cooled water out of the branch line before they get hot water. Therefore, in one sense, PEX has made it harder to do, rather than easier.
01-10-2009, 07:31 PM
Guys, thanks very much for illuminating the recirculation issue. I hope my questions aren't too *stupid* (LOL). I suspected recirculation wasn't a new thing, but I wasn't sure.
I had to laugh when everyone stressed to make sure that the pipes are on the house side of the insulation! ha ha. I get that. It's hard to believe the mistakes a lot of people make that would seem to be "common sense." But working on big jobs while houses are being built installing alarm and home automation stuff, it amazes me how often I'll see things that the "professional" plumber, electrician, or HVAC guy has done that are clearly dead wrong. Then you wonder if they know it's wrong and are trying to "cut a corner" or if they just don't know.
At least with plumbing, it just leaks or don't work right! When you mess up with electric, now THAT can be scary.
When you mess up with electricity the circuit breaker or GFCI usually trips. When you mess up with plumbing you can get a house full of water, and it can be nasty water, at which point you usually do not care if the electricity is working or not. But the guy with the intelligence is usually not in the crew installing the piping, OR the electricity. He is usually out looking for the next project. The guys installing the stuff, are just trying to get the job done and collect their pay. They usually could care less about any problems that are going to happen once they leave the job, whether it is going to happen next week, next month, or next year, and are not interested in doing anything that would making it easier to diagnose or correct those problems.
01-11-2009, 09:12 AM
But the guy with the intelligence is usually not in the crew installing the piping, OR the electricity. He is usually out looking for the next project. The guys installing the stuff, are just trying to get the job done and collect their pay. They usually could care less about any problems that are going to happen once they leave the job, whether it is going to happen next week, next month, or next year, and are not interested in doing anything that would making it easier to diagnose or correct those problems.
Sad but true. This statement comes from many years in the trade. I've seen it in just the little time I've spent OTJ.
01-12-2009, 02:50 PM
I totally agree with the second thing you said, that drive's me crazy.
As for the first thing, I don't disagree with you exactly, I'm just looking at it a different way from all the public safety jobs I've worked for 22 years. Water leaks happen way more often and cause a ton of problems and damage, but the one time a breaker does not trip, people get badly hurt or killed. You can always call the insurance company on a water leak issue...