PEX supply questions

[slremodel]

I have a couple of questions regarding my new PEX plumbing system.

I recently installed a 24 port Manablok with 3/8" supply lines (Plumbing supply store recommendation) to each of my fixtures. The home is only 1800 sq. ft. and I am supplying 2 full baths, kitchen, and a laundry room. I have 3/4" supply coming into the house.

My questions:
1) I am concerned about supplying the kitchen sink and dishwasher (hot) with a 3/8" supply line. The distance from the Manablok to the kitchen sink is about 23'. Should I "T" off the 3/8" to the dishwasher or run a dedicated line to the dishwasher? I'd hate to have low water pressure while the dishwasher is running.
2) The Manablok serves as the shut-off for each fixture. However, after doing some research, I've learned that inspectors(code) require certain fixtures have shut-offs at the fixture (toilets for example). I also plan to have a shut off under the sink for the dishwasher. Will the Manablok individual line shut-offs suffice for all of the other fixtures as far as an inspector would be concerned?
3) I have 3/8" hot/cold running to the showers. I stubbed out the wall with copper from the shower valve. From the valve to the drop "T" (shower head) I only ran 3/8". Is this going to be sufficient? I guess I'd better pressure test before I tile in the bathroom wall.

Thanks.

 

[Jadnashua]

YOu may be dissapointed...3/8" pex has a pretty small interior diameter, and is smaller than 3/8" copper, which by itself is small, especially for things like a bathtub or shower. 1/2" would have been better, and even 3/4" for the high volume things like the washing machine and tub filler. For a sink, it's probably okay.

Can't help you with the other questions...someone will be along in a bit.

 

[Sponsor]

 

[slremodel]

I was afraid that was what I was going to hear. The company I bought the Manablok from made it sound like the 3/8" lines would be sufficient for any fixture since each fixture has it's own dedicated line.

I haven't run the lines for the 2nd full bath or the washer. Is it possible to convert from the 3/8" port to 1/2" PEX line? Worst case, I take down the lines I've already run (have yet to crimp the rings), take the Manablok off the wall and head back to the plumbing store to exchange for a 1/2" Manablok. I'd be out $75 or so for 3/8" PEX parts and line, but I'd rather do it right and ensure enough water pressure when the job is done.

 

[slremodel]

Alright. I'm answering my own questions. After a couple of phone calls and some internet research I've found that they have 1/2" adapters for the 3/8" Manabloc ports. I'm glad I didn't crimp the rings yet. The link below is the Vanguard (maker of Manabloc) supply line recommendations.

http://www.houseneeds.com/Shop/manuals/vanguard_worksheet.pdf

So here's what I'm going to do. I'll take down the few lines I've run and I'll re-run 1/2" to the showers (can't adapt to 3/4"), washer, and kitchen sink. I'll then tee off the 1/2" sink supplies to the dishwasher and the ice maker.

I still need to know about the fixture shut-offs. Also, can someone confirm that what I plan to do is the best way?

Thanks!

 

[Jadnashua]

I think you'd be better off with a 3/4" manafold, and convert to 1/2" for those areas you don't need to volume. Best to wait for the real pros to show up, but if you do some searches here, I think that is what you'll find. Note, something like a vanity sink probably would be fine with 3/8", since it and may items are flow restricted.

 

[slremodel]

I should have done the research before I posted a new thread. Hopefully this will be helpful to someone else.

The Manabloc specs list a 2.5 GPM rating for 3/8" PEX. See below.

From everything I've looked into, all new shower heads have a max of 2.5 GPM (Energy Policy Act of 1992). If that's true, I may be okay to keep 3/8" to all my fixtures.

This comes from the aquastar tankless water heater website.

How many gallons per minute (gpm) are used by a shower, a sink, a bathtub, etc...?
As stated by the Department of Energy: shower = 2.5 gpm; sink = .5 to 1.5 gpm; washing machine = 2 gpm; dishwasher = 2 gpm.

It looks like I'm alright to use 3/8" PEX throughout the house. I will probably run a deicated line to the dishwasher rather than "T" off the existing 3/8"

Still no answer on the shut-offs.

 

[Jadnashua]

Ever notice how if you put your finger over the hole of the hose, you can get the spray to go a lot further than if you just let it flow? Now, picture that for your showerhead...if the fixture can flow all of the water that is available, you may not like the results.

Take a washing machine - 2.5gallons/minute, unless it is a front loader water saving one, you're talking about 15-minutes to fill some of them. Yes, it will work, no, it may not be the best. A nice soaking tub can hold 40-60 gallons - a tub filler can flow as much as 8-9 gallons per minute depending on the design, with probably 6-7 more average. By th etime the tub is full, it has cooled off at 2.5gpm.

 

[Master Plumber Mark]

3/8 PEX is a joke

for just a very little bit more $$
you could run 1/2 PEX everywhere
and not worry about this whole situation......

with 1/2 PEX you could tee off at the kitchen
hot line and run both kitchen and DW off the same
line

if you are going by anything
that Aquastar tankless water heaters is claiming will work,
then you are in for big troubles and down the road you wont be happy.....


their unit will only work with restricted flow
through the pipes....
just look at all the complaints about them out there


and I would be very concerned about volume for 2
showers going at same time through that
3/8 manifold..


I could almost piss a stream that would match
3/8 PEX pipe -----on a good morning...LOL


I say go a little bigger or stay home

 

[Bob NH]

Copper is expensive so people want an alternative.

PEX is new, snazzy, and expensive, so a lot of people who are turned on by that sort of thing will buy it.

But 3/4" CPVC throughout the house will be a whole lot less expensive and give better flow.

And if you need even more flow you can get CPVC in larger iron pipe sizes, such as 1" IPS. But you can't get 1" at Big Orange.

 

[Cass]

3/4" manablok and change PEX pipe to 1/2"

You will be a whole lot happier when this is over, the cost is minimal.

1 other question, do you know what your water pressure is?

 

[hj]

Pex

I haven't used a ManoBloc system, but have been in many houses that do have them, and have not seen ANY individual shutoffs, even on a toilet, other than the ones on the manifold. I will say that I am not impressed with the quality of the manifold valves. They seem to have a high failure rate if they are operated too many times.

 

[slremodel]

Thanks for your responses. They have been very helpful. I have a similar mentatility like that of Mark the Master Plumber's in that if you can go big, why not? However, I also don't think it's necessary to take your grenade launcher rabbit hunting.

I found this about the Manabloc supply lines. I will need 1/2" for the high demand lines (i.e. the bathtubs and the hose bibbs)

I should clarify that the Manabloc has a 1 1/4" main bore with 3/8" ports. Not a 3/8" main bore. Therefore running two showers at one time shouldn't be a problem. We have 3/4" running to the Manabloc.

From vanguard
"The system distributes water efficiently and economically. By sizing the lines according to the demand of each fixture, homeowners enjoy much faster hot water delivery which results in significant water and energy savings. The 1 1/4" reservoir in the MANABLOC maintains more consistent supply of water pressure reducing the potential for drastic temperature changes at fixtures; even when other fixtures are operated simultaneously. The performance of a conventional plumbing system during multiple fixture operation can't compare to a MANABLOC system".

Lastly, I think I'll put in shut-offs at the toilet fixtures and the dishwasher. Other than that, I'll rely on the Manabloc shut-offs. I am slightly concerned with the long term functionality of the Manbloc valves. Then again, my old fixture valves seemed to drip after only one a few uses anyway.

I'll be sure to let you know the outcome of the install.

Thanks again!

 

[Cass]

Remember,. the ID of the 1/2" PEX is smaller than 1/2" copper. What is your water pressure?