PEX Plumbing Part 5, MANIFOLDS

I have received many questions from my guides on PEX plumbing. One of the most asked is about manifolds. This guide might get a little long but I hope to answer as many questions as possible. I have also found an E-bay seller that has the type of manifold I used in my system.

First let’s start with a general definition of the word manifold, 1) Consisting of or operating several devices of one kind at the same time. 2) A pipe or chamber having multiple apertures for making connections. More simply put, for plumbing, it is a control center for hot and/or cold water that feeds “flexible plastic supply lines” (PEX) to individual fixtures. Please note that in my guides I am addressing potable (drinking) water PEX systems. A lot of the same information applies to radiant heating systems but these are usually found under floors and have differences in installation.

There are many benefits to the PEX manifold system. 1) Because most of the connections are made at one central point, any leakage is visible and easier to correct. 2) Individual branches of the system can be shut off for service without shutting down all of the water to the system/residence. 3) This system provides a much more regulated water pressure supply!

To understand the improvement in water pressure picture yourself with a 50′ or longer garden hose. This hose has holes, of equal size, every five feet or so from the faucet handle to the end of the hose. The first hole in this series will have the largest, strongest, spray of water. As it continues down the hose each subsequent hole has slightly less pressure spray until it gets to the end where you are trying to water your garden and muttering under your breath. Now picture this same hose, with the same number of holes, but now those holes are all only a few inches apart and very close to the end of the hose. Each of these holes still leak but the pressure at each is more consistent and you have pressure to water the garden. Your home plumbing system is actually quite similar to this. Of course if you have tried this little experiment you are now very wet and need a new hose!

Remember that your water pressure will be dependant on the incoming service line.

Types of manifolds: There are many different types of premanufactured manifolds available from many different suppliers. They also had a wide range of prices. The MANABLOC is one type that has both hot and cold lines in one compact unit. They are available in different Pex line sizes and a large number of different configurations for hot and cold outlets depending on the number you need. Plan on spending well over $100 for this type of unit.
( see photo )

Next is a much more simple version. These also are made by different manufacturers and are available with several different number of outlets. With this straight line type of manifold you would place one for your cold water supply lines and one on the outlet of the hot water heater to supply your hot lines. Some are closed on one end and some are open on both if you need to continue the run. They are available with and without shut-off valves attached. This is the type I used for my home and I added my own shut off valves. I used this system to allow me to add more plumbing lines later if needed. ( photo two )

Now for the manifold I assembled. It may not be very pretty but it works great and again, I am NOT a plumber! ( Photo three )

This single type of manifold is MUCH less expensive and I have found one E-bay supplier, so far, that seems to have a good variety and very reasonable prices. See user: hydronicwarm This link takes you to his listings Note: I did not purchase from this seller because I did not find his listings at the time of my purchase. (If you also supply manifolds at good prices I will be glad to add you into my list.)

I have also been asked if making your own manifold from scratch is possible. Yes, it is.

1) You can create the same effect with 1″ or 3/4″ PEX with numerous “Tee” connectors and valves in a short series. The drawback to this is that it would require a large number of connectors and crimps for those connectors. The more connections you make the more potential leaks that can occur.

2) If you are a GOOD machinist you could very easily create the same type of copper manifold. Note that I said GOOD machinist. I am not one! First you would need a piece of copper piping 3/4″ in diameter cut to the length you want. You would then need to attach, by soldering, a 3/4″ PEX female solder connector on one end. You would need to drill the appropriate size holes, equally spaced along the tube to accomodate the needed number of 1/2″ PEX outlets you want. Close the other end by capping. This is actually the type I purchased, hand made, from a machinist. It works wonderfully but I would not try this myself.

Finally, on mounting your manifold. They are lightweight and can be installed just about anywhere that will accomodate your particular size manifold. The important things to remember here is that you will need to be able to access the manifold and the valves! This means don’t bury it in a wall. If you are using a thermoplastic type manifold it is recommended that you have at least a 36″ vertical clearance and 18″ horizontal clearance from your hot water heater. This is not needed with copper manifolds because the PEX itself can handle the heat. You may also want to label each different outlet branch on the PEX so you know later what each line is supplying.

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