Advantages of a Plumbing Manifold System

by Margaret · Published March 13, 2019 · Updated October 11, 2019

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Originally this post was “decide between a plumbing manifold system and a trunk and branch plumbing system.” That is, until I started writing it. I seriously tried to be fair to a traditional branch plumbing system.

I really did.

In the end, it morphed into “why you must have a plumbing manifold if you are even dreaming about a new home build or a remodel”. This isn’t your average argument–read on for subtle, yet mind blowing reasons I didn’t know existed until the International Builder’s Show last month.

A plumbing manifold system is easy to service.

A manifold is right there. No hidden junctions, no mysterious branches in your walls.

Need to replace a faucet? Go for it! Simply shut off the hot and cold water lines to that individual faucet. You can still go to the bathroom in the meantime.

Want to add a utility sink or a wet bar? Add one here! Bonus if you allowed for expansion and have a pre-run line like we did in the manifold described in this post.

Where is a traditional trunk and branch system? Hidden in your walls. You only have a shutoff for the whole house…

and another on the supply side of the hot water heater.

Need access to anything else with a traditional plumbing system?

Good luck.

Maintain water pressure

A manifold is more likely to maintain water pressure when multiple endpoints are in use.

Remember shouting in a shower when someone flushed the toilet?

We weren’t cheering for our trunk and branch systems at that point. Just yelling at our brother to stop flushing!

The ‘D’ shape of the cold water manifold is designed to maintain water pressure when multiple lines are in use. When someone is watering plants outside on the bottom, larger 3/4″ line toward the beginning (bottom) of the manifold, there is still some water pressure for someone to wash hands in the kitchen at the top of the manifold. This is due to the two sources of water feeding opposite ends of the entire lineup to better maintain water pressure.

Plumbing Manifold Advantages – Maintain Water Pressure

Have a leak? A manifold plumbing system buys you time.

You are nodding your head if you ever had a leak or an unexpected repair in the past with a hidden trunk and branch system. Water is spewing everywhere and you are madly trying to shut it off at the main, if you are lucky, or cursing as you attempt to turn the valve on the city meter.

In essence you are shutting off the water to your house and you are caught scrambling for a solution. If you have a slab leak you have to call someone out to mark where the lines run under the house. Then you decide if you want to do the repair yourself, as a DIY’er, or you call a plumber.

Either way you are out time and without water.

There are few things I hate more than making a rush decision and regretting it later.

In my case, the hot water line burst connecting the water heater to the two bathrooms. If I had a manifold system instead of a trunk and branch system the slab leak would have been no big deal. I could have continued to use one shower, the kitchen sink and dishwasher instead of having to shut off hot water to the entire house.

Do you seriously think you’ll use less hot water with a trunk and branch plumbing system?

Some people are going to argue it takes longer for hot water to get to a faucet on a manifold system versus a trunk and branch system.

Last I checked, I don’t wash my hands after I get out of the shower. Likewise, I don’t go around turning different faucets on and off on one end of the house. I do my business with a single faucet and move on for at least an hour.

By the time I do need to wash my hands again, the water in the line is going to be cold anyway. So the water still has to get blown out to get hot water–in both a manifold and a branch system.

If you or I use the bathroom more than once an hour it is commonly due to dire circumstances and it is short term…

Another argument is a manifold could CLEARLY use less hot water given the situation below. I’ll be taking my own home for a real example where two bathrooms are on one side of the house, far, far away from the water heater:

In this case the hot water has to go the two legs of a right triangle to get to the master bedroom in this trunk branch system. A manifold can take the hypotenuse. The water would get to the master shower SOOOO much faster.

It’s also exacerbated by the fact that now BOTH bathrooms are affected by the additional 16′ bypass put it when the hot water line burst and we ran PEX through the attic. Only one of the five lines (two shower heads and three sinks) would suffer this awful extension as opposed to ALL of them..if I had a manifold.

In this scenario, hells to the yes, you would use less hot water with a manifold. A manifold may use less hot water than a trunk and branch system due to direct plumbing runs.

Detect the source of water leaks faster.

You may have noticed my excitement over the whole house water usage systems offered by Uponor and Moen. The fact that I have been the recipient of an under slab rolled copper pipe leak might have something to do with it…

In any case, both companies claim they can detect as little as one drop a minute. Early detection, easily done with these systems, is key to preventing your average $7,500 water damage claim.

Detecting a drop is great, but how do you determine the source if the leak is in the walls or under the slab–places you can’t easily see?

I have a trunk and branch system in my house and even if I install this fantastic monitoring system, there’s no way I would know which line is dripping, much less where. So the system would tell me something is happening but who the hell knows WHERE it’s happening.

These whole house monitoring systems should make you feel empowered and safe. Instead, you are sitting there waiting on pins and needles for who knows how many days/ months/ years. You still need the leak to get strong enough to detect the location:

a stain or bubble in the wall,
tiles start popping on the floor, or
hire a forensic plumber to come scan as the leak gets stronger.

All terrible options!

I hate to say it, but ignorance is bliss. I’d almost rather save the money and not know.

You actually do want this in place. When the leak goes from a drip to carving the Grand Canyon under your house, the monitoring system detects the unusual activity and shuts off the water by itself (a follow on post explains how it doesn’t shut the water off of a unexpectedly long shower). It will send you a notice and be patiently waiting for you to arrive home from work, or even worse, your vacation.

The thought of spending a decent amount on a monitoring system ($499-$850) that can’t tell you where the slow start of a problem is located kept bothering me. That is, until I had a Eureka! when we stopped to use the trunk and branch supplied bathroom at Basha’s in Wickenburg on our way home from the International Builders Show: A MANIFOLD SYSTEM!

If you have a plumbing manifold system you can turn off every last run and manually run the diagnostic check one line at a time until you find out which one has the slow drip!

SOLD!

Seriously–read that last sentence again–this is where home improvement gets exciting!

I *KNOW* I got lucky with my slab leak. Now I MUST have a manifold AND a Phyn, Flo, or whatever the best monitoring system is at the time in my next house.

You save plumbing material with the install of a trunk and branch plumbing system.

This is the one argument where a trunk and branch plumbing system clearly wins. I’ll admit to cutting material usage close (“close” probably isn’t the right word on how nerdy that post got).

Want instant heat?

A manifold is not the answer for you.

However, in light of our last point on a trunk and branch system costing less, a re-circulation loop on a trunk and branch system increases the amount of materials used in addition to the constant heating and cycling of water in the line.

Here is where you decide what matters to you:

minimal initial cost or…
the convenience of accessibility, detecting problems and slow repairs.

Now you can see why this turned into more of a “why you need a plumbing manifold” post. If you still opt for a trunk and branch system I’d love to hear why. Or, if you are like-minded and have other advantages for a plumbing manifold system I want to hear from you too!

Convinced you want a plumbing manifold now? Check out these posts to read about more manifold goodness:

Or to get a visual of these advantages in person, watch this video: