Author Topic: couple of plumbing questions  (Read 11320 times)

Offline bevans6

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couple of plumbing questions
« on: June 01, 2009, 07:05:08 AM »
new bus has a 120VAC or propane water heater.  Propane is not hooked up, since the water heater is currently installed inside the luggage bay.  The question is, how do people normally install propane hot water heaters into buses (MC-5C).  The luggage bay is where all the rest of the water system is, but it seems poor practice  to not have the propane side open to the outside all the time.  Do people simply forego having a propane water heater, or do they cut a hole in the side of the bus to install it open to the outside as with a normal RV?

Second question - venting the grey/black tank.  My tank appears to be vented to the underside of the bus, or into the rear axle space, which I suppose is technically the underside.  I think that would be acceptable for a grey only tank, but I think that a black tank needs more venting and the vent should be on the roof.  What is the advice?

Thanks, Brian
1980 MCI MC-5C, 8V-71T from a M-110 self propelled howitzer
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Tatamagouche, Nova Scotia

Offline Len Silva

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Re: couple of plumbing questions
« Reply #1 on: June 01, 2009, 07:51:18 AM »
If you are going to use an RV propane water heater, then yes, the only option is to cut a big ugly hole in the side of your bus.

If, on the other hand, you want to stay with electric, then I would replace it with a the largest electric water heater you can fit in the bay.  I had a 20 gallon unit and even after a day or so without power, you could still get a couple of quick showers (in moderate weather, of course).

As for the tank vent, if it ain't broke, don't fix it.  If you do have an odor problem, then consider taking it up through the roof.

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Offline Utahclaimjumper

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Re: couple of plumbing questions
« Reply #2 on: June 01, 2009, 08:09:53 AM »
I have a neat hole covered in mesh for the heater, painted to match its not obvious.>>>Dan
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Offline Sean

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Re: couple of plumbing questions
« Reply #3 on: June 01, 2009, 08:49:57 AM »
If you are going to replace the LP water heater, as Len suggests, then you might consider a marine model with a heat exchanger.

These units will run on 120VAC when it is available, but can also be plumbed into either a house hydronic system if you plan to have one, or, if not, directly into the engine coolant loop.  I would tee off the heater take-off and put a gate valve in line to control how much coolant flows through the water heater vs. forward to the heaters.  With this arrangement, you will get free hot water while you are driving.

As for your waste tanks, they are required to be vented through the roof.  In addition to the tanks being vented this way, every fixture drain must also be vented to the roof.  Separate vents are not necessary -- vent pipes can be combined below the roof line, so long as they join above the flood rims of their respective fixtures.

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Offline busshawg

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Re: couple of plumbing questions
« Reply #4 on: June 01, 2009, 09:17:36 AM »
I pondered the same question re your hot water heater for quiet sometime. I actually mounted it in the rear cargo bay with my water, after quite sometime I broke down and mounted up in the side with that big ugly hole that Len is talking about. The hot water tank now sits in my lower kitchen cabinets and is vented to the outside at all times. I am happy with the installation.

As far as venteing goes, I agree , if it's not broke don't fix it. However if you are getting fumes it's broke.
I vented mine staight up through the roof. The pipe runs through a bathroom floor to ceiling closet. Works well.

Grant
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Offline Tenor

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Re: couple of plumbing questions
« Reply #5 on: June 01, 2009, 10:38:40 AM »
I have done all of these things successfully.  I have a propane hot water under my kitchen sink vented to the outside.  I also have a marine unit just like Sean describes plumbed into the heater loop.  I put valves on the water lines so that I don't have to shove my hot water from either source all the way through the one that is not being used.  I vented my black water tank through the passage behind the fridge and out the plastic cap of the fridge vent.  Didn't need an extra hole in the roof.  I sent the grey water vent through the rear wheel well.  No smell in the first year of use.

Glenn
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Offline TomC

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Re: couple of plumbing questions
« Reply #6 on: June 01, 2009, 03:43:02 PM »
The setup I have is two 10 gal water heaters straight from Home Depot (no heat exchanger).  One is plumbed to the next with the final one run through the inverter for heat during the day going down the road.  I like it so much, I'm using the same setup on my next conversion.  Except for draining once a year, no maintenance in the 14 years they have been in.  Plus they are cheap.  Good Luck, TomC
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Offline gmpd4104

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Re: couple of plumbing questions
« Reply #7 on: June 01, 2009, 04:55:22 PM »
as mentioned think about a marine unit.

Marine units are built with vibration and jaring in mind and with the heat exchanger you can get several showers with SUPER hot water right after driving and as also mentioned well after stopping too.


Offline gus

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Re: couple of plumbing questions
« Reply #8 on: June 01, 2009, 07:57:05 PM »
Bottom waste tank vents work fine, both black and grey. I have this setup and so do quite a number of others. Sure beats a hole in the roof.

Just make sure it has a loop that carries it above the waste liquid level.

A bottom vent also serves as an overflow.
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Offline Sean

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Re: couple of plumbing questions
« Reply #9 on: June 01, 2009, 09:02:01 PM »
Bottom waste tank vents work fine, both black and grey.

Works fine, right up until it doesn't, and then your coach explodes from methane build-up, or you get killed due to some other noxious gas.

This is the reason why it is not allowed.

Quote
7.7.6.1 Roof Extension. Except as otherwise permitted in this standard, each vent pipe shall pass through the roof and terminate vertically, undiminished in size, not less than 2 in. (50.8 mm) above the roof. Vents terminating on curved roof recreation vehicles or recreation vehicles with elevating tops must pass through the roof or upper side of the recreation vehicle at a point as high as practicable and not less than 6 ft from the ground level.

(Forgive me, my code book is a bit out of date.  The above is from the 2002 edition.)


Quote
A bottom vent also serves as an overflow.

Overflows are not permitted on waste tanks.  That opens up the possibility of putting raw sewage on the ground.

FWIW.

-Sean
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« Last Edit: June 01, 2009, 09:05:47 PM by Sean »
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Offline bevans6

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Re: couple of plumbing questions
« Reply #10 on: June 02, 2009, 06:41:37 AM »
Sean, what code book are you referring to?  I think I'd like to get a copy.

Thanks everybody, I appreciate the help and advice.

Brian
1980 MCI MC-5C, 8V-71T from a M-110 self propelled howitzer
Allison MT-647
Tatamagouche, Nova Scotia

Offline Sean

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Re: couple of plumbing questions
« Reply #11 on: June 02, 2009, 08:08:59 AM »
Sean, what code book are you referring to?  I think I'd like to get a copy.

ANSI/NFPA 1192, which covers everything in an RV except the electrical systems (which are covered in the National Electric Code, NFPA 70).  Lots of good information not only on waste and water plumbing, but also LP (propane) systems, emergency exit requirements, "toy hauling" compartments, heaters, and more.

It can be downloaded in PDF format from NFPA or ANSI for about $35.

-Sean
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Offline gus

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Re: couple of plumbing questions
« Reply #12 on: June 02, 2009, 01:26:00 PM »
Why would methane build up in a bottom vented tank any more than in a top vented one as long as the vent is open?

If the vent is plugged there is no difference.

Does this code book apply to bus private bus conversions?

If a waste tank overflows where does the excess go?
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Offline Jerry32

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Re: couple of plumbing questions
« Reply #13 on: June 02, 2009, 01:41:27 PM »
Code book always rite so mone all go through the roof. certainly was not a problm to do as i designed to pass through a closet. Jerry
1988 MCI 102A3 8V92TA 740

Offline JackConrad

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Re: couple of plumbing questions
« Reply #14 on: June 02, 2009, 02:27:42 PM »
If a waste tank overflows where does the excess go?

If you have a combination waste tank that is installed properly with a vent through the roof,  the tank will back up into the shower (lowest opening the the contents can escape through), If you have a separate black tank, when you try to flush the toilet (RV type), you will see tank contents in the bottom of the toilet.  Jack
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