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Author Topic: Fresh hot and cold water circuits in a bus  (Read 4487 times)
bryanhes
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« Reply #15 on: July 29, 2010, 09:25:27 PM »

Jim,

I have seen that one before and like the set up.

BG6,

Wouldn't you have better pressure if your lines in your coach are smaller than the feed to the manifold?

That has been what I have always seen anyway. A larger feed to the manifold and then reduced from the manifold for more pressure.

Bryan
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kyle4501
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« Reply #16 on: July 30, 2010, 05:34:21 AM »

The reduced line size adds to the pressure drop. Line sizes are reduced after a manifold to help even out the flow to each circut.

If all lines are the same size, the shortest run would 'steal' all the water whenever it was used (assuming there wasn't much restriction in the fixture).

In an 'ideal' system, each branch would have more flow capacity than the fixture & the total capacity of all the fixtures combined will be less than the capacity of the supply to the system.
Adding a pressure regulator to the inlet will also help reduce flow deviations. As flow from the supply increases, the supply pressure drops. If the pressure regulator is set at or below what ever this pressure is at full flow, then the pressure seen by the individual fixture won't change no matter what other fixture is used. This also assumes the regulator is big enough that it doesn't restrict flow.  Cool
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rv_safetyman
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« Reply #17 on: July 30, 2010, 06:57:54 AM »

Concerning water "regulators".  The cheap ones you get from an RV store are not regulators.  I bought a true regulator (Watts 263A).  After I first installed it, I ran into a park that had very high water pressure and the Watts seemed to do its job.  I tried it later at another park and the pressure was again high, but the regulator did not regulate the pressure.  I did a quick read about these units and they seem to be sensitive to water quality and are easily compromised.  They can be rebuilt, but I did not take the effort.

Instead, I always use my on-board water pump and only use the park water supply to fill the tank. 

I am paranoid about over pressure.  I used Qest fittings with pex tubing and they work well, but I don't want to push my luck.  A blown line while we are away from the bus would be a problem.

Jim
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Jim Shepherd
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kyle4501
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« Reply #18 on: July 30, 2010, 07:56:28 AM »

In industry, using multiple regulators is common - especially when you are taking big reductions in pressure. They step the pressure down to limit the max pressure the last regulator sees.

Using an on-board water pump all the time definitely has advantages.  Cool
I've often thought having the pump controlled by an off-delay relay (with a momentary on switch at each fixture) would ensure it is off when not needed & reduce the impact of a leak in the supply line.  Grin
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« Reply #19 on: July 30, 2010, 08:06:29 AM »

Kyle, I have toyed with some sort of pump switch as well.  In an early camper, we came close to having a fire, because the water pump froze up and the motor overheated.  Like you, I worry about a line breaking and the pump flooding the area.

We have our pump on a single breaker/switch that is very convenient to turn off, but we forget.  I had thought about (and bought but didn't install) a standard 120V rotary timer switch.  When you wanted water you would simply turn the knob to the amount of time you wanted and then it would shut off automatically.

I have this picture in my mind that it would shut off when Pat was in the shower Shocked Shocked  Sort of funny for the first few seconds Roll Eyes

Jim



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Jim Shepherd
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Bus Project details: http://beltguy.com/Bus_Project/busproject.htm
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« Reply #20 on: July 30, 2010, 08:20:45 AM »

In my bus, I used Qest plastic lines and fittings.  While it has been 100% reliable, I also had copper/brass ball valve manifolds made for both the cold and hot, with one ball valve per water usage.  Now on my truck, like Jim, I'm going to use the Pex manifold system-far cheaper and readily available.  I am going to stay with two water pumps-while both also have been 100% reliable-when someone is showering and the other is doing dishes, running both water pumps makes for seamless water pressure where the one showering doesn't feel the difference in pressure.  It just involves having two water pickups out of the water tank, but then you're having the tanks custom made in most instances.  Good Luck, TomC
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06 Bill
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« Reply #21 on: July 30, 2010, 08:30:33 AM »

Kyle  Square D makes a low pressure cut off switch that trips below a set (adjustable) pressure and must be manually reset after repair.
Normal cut out & cut in pressures also adjustable. Catalog # FSG2J20M4CP     06 Bill
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kyle4501
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« Reply #22 on: July 30, 2010, 08:31:07 AM »

. . . I have this picture in my mind that it would shut off when Pat was in the shower Shocked Shocked  Sort of funny for the first few seconds Roll Eyes

That would definitely encourage less time in the shower!  Shocked

& possibly more time in the dog house  Roll Eyes
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« Reply #23 on: July 30, 2010, 08:43:29 AM »

Kyle  Square D makes a low pressure cut off switch that trips below a set (adjustable) pressure and must be manually reset after repair.
Normal cut out & cut in pressures also adjustable. Catalog # FSG2J20M4CP     06 Bill
Thanks, but the thing I think I want is almost no pressure in the supply lines when we aren't using water. Maintaining a pressure head takes energy & if it isn't needed, why spend it?
We are practicing this now with the TT (tin turd Airstream) which has only 30 gallon waste tanks (a 30 black, & a 30 gal grey).
Another concern I have is 'wasting' water as I want to be able to boondock as long as possible for a given tank size.

But, I'm still a ways off from building my system, so the plan will continue to evolve in the mean time.  Wink
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« Reply #24 on: July 30, 2010, 08:49:45 AM »

We just shut the pump off while we are away from the coach. Pressure usually bleeds back through pump to zero anyway. 06 Bill
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BG6
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« Reply #25 on: July 30, 2010, 09:30:34 AM »

My factory built Airstream trailer has 3/8" poly tubing daisy chained (And, from the looks
The advantage of a manifold system is you can select which circuts are used - may be usefull if you want to isolate one fixture. I'm thinking it may clean up the plumbing under the sink too. (But, if you need to shut off the supply to a fixture, you're going to have to do it at the manifold, not the fixture.)

The only time you are going to need to isolate one fixture is if it breaks on the road.  If you avoid the plastic Wally World junk, and properly support your PEX lines (clamps on the wall) this won't happen.

Every added fitting or valve induces turbulence -- which reduces flow and pressure.  It makes no sense to me to spend the money on manifolds and valves, when all they do is make low park pressure worse.

My system is simple.  Water comes in from the hose fitting and goes to the filter, with a tap for the toilet.  The filter has a valve, so I can cut off all other water and still be able to flush the toilet.  From the filter, the cold line goes to the kitchen faucet, with a tap to the water heater inlet and the tub and shower valves.  Ts on the water heater fittings serve the washing machine, and the hot line feeds the tub and shower on the way to the kitchen sink. 
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Chaz
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« Reply #26 on: July 30, 2010, 10:35:24 AM »

Tom,
 I have a spare water pump that I was wanting to add to the system to try to solve my shower temp. issue. What do you think is the best way? Parallel? Series? Seperate line? I'm hoping I can make it a quick easy fix for now. When I do my new cabinets, I'm going to move the H20 heater a LOT closer to the tank and will re-work some of the plumbing.
  Thanx,
    Chaz

p.s. Been wanting to ask you if you have a recent pix of the "truck"? Expiring minds are nosey.  Grin Grin Grin
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kyle4501
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« Reply #27 on: July 30, 2010, 11:02:21 AM »

I'm glad yours works for you.  Grin
But, sometimes I want to use my RV in cold weather - minimizing the water in the system that has to be drained before bed time has some advantages.
 
Some floor plans have everything close together, so a branch system is easy.
Some like to have a recirculating loop to keep the hot water at the tap hot - that would be easier to do with a branch system.
My floor plan has a full bath near the rear & a kitchen at the front along with the original washroom (that I'm keeping), so a home run system works better for me.

Also, with the manifold system, there are no fittings anywhere except at the manifold & fixture.  Cool
You will have fewer tube ends with a manifold than with tee fittings (each tee has 3 tube ends), & we all know every fitting is a potential leak.  Shocked .
If the manifold is sized properly, there won't be any noticeable flow or pressure loss.
I will have stop valves for every fixture, so that combined with fewer fittings goes a long way towards the cost of the manifold.  Wink


FWIW, Based on my planned fixture location for 1 1/2 baths + kitchen, the manifold with integral stop valves has 32 fewer tube ends. So each method has advantages, it all goes back to what works best for the whole system design.  Grin

As always, YMMV

 
My factory built Airstream trailer has 3/8" poly tubing daisy chained (And, from the looks
The advantage of a manifold system is you can select which circuts are used - may be usefull if you want to isolate one fixture. I'm thinking it may clean up the plumbing under the sink too. (But, if you need to shut off the supply to a fixture, you're going to have to do it at the manifold, not the fixture.)

The only time you are going to need to isolate one fixture is if it breaks on the road.  If you avoid the plastic Wally World junk, and properly support your PEX lines (clamps on the wall) this won't happen.

Every added fitting or valve induces turbulence -- which reduces flow and pressure.  It makes no sense to me to spend the money on manifolds and valves, when all they do is make low park pressure worse.

My system is simple.  Water comes in from the hose fitting and goes to the filter, with a tap for the toilet.  The filter has a valve, so I can cut off all other water and still be able to flush the toilet.  From the filter, the cold line goes to the kitchen faucet, with a tap to the water heater inlet and the tub and shower valves.  Ts on the water heater fittings serve the washing machine, and the hot line feeds the tub and shower on the way to the kitchen sink. 
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TomC
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« Reply #28 on: July 30, 2010, 12:47:45 PM »

Chaz-I have the two water pumps Y'd into a single 3/4" supply line to the cold manifold-which also has the feed for the water heaters.  Using the pumps in parrallel you increase the flow, but not the pressure.  If you have one feeding into the next (in series) you'll increase the pressure but not the flow.  Since the pumps put out around 40psi, if you ran in series, you'd have at least double the pressure at 80psi-a bit to high.

I will post picts of the truck next week-just had the interior spray insulated.  Thanks, TomC
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Len Silva
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« Reply #29 on: July 30, 2010, 01:11:01 PM »

If you really want to conserve water, use a manual pump in the shower. Cheesy
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