Bilge Hose size problem

jssailem · Jan 29, 2020

One of the hydraulic engineers here on the forum can share the realities of turbulence in a closed system, but generally, if pumping from a 1 1/8 ID to a 1 1/2 ID hose you are pumping from pressure to less pressure (High to Low), should be ok. If you were going in the opposite directions you would be creating higher pressure and that would not be good.

Ralph Johnstone · Jan 29, 2020

No problem in going from a smaller diameter hose to a larger diameter outlet. Other way around .............. ?? requires a few calculations.

jssailem · Jan 29, 2020

Ralph Johnstone said:
No problem in going from a smaller diameter hose to a larger diameter outlet.

YEA

my professor would be pleased that I listened to his lectures... and can still remember.

Ralph Johnstone · Jan 29, 2020

ontherocks83 said:
if there was some taboo secret I didn't know about using a male to male adapter that somehow restricts flow.

No problem with male to male hose fitting when properly clamped.

ontherocks83 said:
Also if anyone is up for additional questions, should I put an anti siphon valve in the high loop when I run it?

If you are discharging at a high level above the waterline, no need for an antisiphon as there's nothing to suck back.

jssailem · Jan 29, 2020

A 12 inch loop above the discharge would not hurt, anti-siphon should not be necessary. Note you will get the water from the pump to the top of the loop to flow back into the bilge. It is the nature of the Rule "in bilge" pumps.

rgranger · Jan 29, 2020

ontherocks83 said:
I know small to big isn't the problem I guess my concern was the actual adapter, if there was some taboo secret I didn't know about using a male to male adapter that somehow restricts flow.

Also if anyone is up for additional questions, should I put an anti siphon valve in the high loop when I run it?

Isn't the limiting diameter the I.D. of the adapter?

Ralph Johnstone · Jan 29, 2020

ontherocks83 said:
It is in the transom above the static water line but is very close when under power, going fast, or in following seas

Should have an internal loop if you're getting that close while under way. Siphon breaker ............ flip a coin to see if you should use one.

rgranger said:
Isn't the limiting diameter the I.D. of the adapter?

The length of the adapter is so short that any additional friction head (due to increased velocity) will be minimal.

JamesG161 · Jan 29, 2020

It is the friction loss that reduces pump flow.
Bigger Diameter of hose is less friction loss or more flow.

Expansion of Flow at the pump is best.
Make everything 1 1/2" from pump to discharge.
The adapter, at the pump, is minimum friction loss.
Jim...

Jim26m · Jan 30, 2020

JamesG161 said:
It is the friction loss that reduces pump flow.

And lift or static head...

Jim26m · Jan 30, 2020

ontherocks83 said:
I am replacing my existing bilge pump and hose in my boat. I am putting in a Rule 2000 gph pump that has a 1 1/8" discharge outlet. The problem is my thru-hull in the transom has a 1 1/2" nipple. Is it ok to use a hose adapter like this to make the hoses fit?

MarineEast Hose to Hose Splice/Adapter

Features: Hose Barb to Hose Barb Splice/Adapter A Real Problem Solver Applications: Marine Sanitation Hose Black Plastic Cuts installation time and labor Molded of high-strength engineered plastic Note: Images shown are for illus

www.defender.com

I am adding a second rule 2000 and have to drill a new thru hull so for that one I will just use a 1 1/8 thru hull to match the pump.

The alternatives I could think of but would prefer not to is to either change out the existing thru hull, or upgrade the pump to a rule 3700 gph that has a 1 1/2 discharge but those go for about $200 a pop.

The hose barb adapter should be fine in the manner you intend to use it. As noted above, there should be minimal pressure loss associated with this application.

Ralph Johnstone · Jan 30, 2020

JamesG161 said:
Expansion of Flow at the pump is best.
Make everything 1 1/2" from pump to discharge.
The adapter, at the pump, is minimum friction loss.

Jim26m said:
And lift or static head...

Excellent ! EXCELLENT

!!

Now who would like to explain how velocity head poses another resistance to flow rate and how that increased velocity (in the coupling) never returns 100% of its velocity energy to pressure energy once the restriction (coupling) has been passed ?

On second thought, I'm no longer getting paid to teach this crap so go figure it out for yourself

.

And that was a looooooooong time ago. Funny how you can remember stuff like that which you no longer use but my wedding anniversary,

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rgranger · Jan 30, 2020

Ralph Johnstone said:
On second thought, I'm no longer getting paid to teach this crap so go figure it out for yourself .

I'm not quite there yet....

JamesG161 · Jan 30, 2020

Ralph Johnstone said:
100% of its velocity energy to pressure energy once the restriction (coupling) has been passed ?

The normal return to fully developed, standard flow is 10 x Inside diameter of hose.

Example: Say inside hose diameter is 1 inch. Then 10 x I inch = 10 inches from the discharge of pump adapter.
____

Jim26m said:
And lift or static head...

That is a constant for sea water and a bit more flow for fresh water. All Rule pump curves use fresh water and...

12VDC at the PUMP!

If your new bilge pump wiring is not sized right or low battery, then your flow drops.
______

Ralph Johnstone said:
I'm no longer getting paid to teach this crap so go figure it out for yourself

rgranger said:
I'm not quite there yet

I still practice so I can...

Preach

Jim....

Ralph Johnstone · Jan 30, 2020

rgranger said:
I'm not quite there yet....

My condolances.

I did it for six years in between real jobs and really got a kick out of it when I could see the light go on in some kids eyes at the back of the hall. As much as I enjoyed it, it just didn't pay the bills so well.

Went back into industry and finally semi-retired at 51. Give it a try. I wish I had dumped the full time stuff 5 years earlier as it's really not that difficult. The money I mean, not the obvious stuff.

Ralph Johnstone · Jan 30, 2020

JamesG161 said:
I still practice so I can...

................. remember

? ? ? ?

JamesG161 said:
The normal return to fully developed, standard flow is 10 x Inside diameter of hose.

Yes, we may be back to the original flow pattern but it's the permanent energy loss due to the higher velocity fluid not being able to return 100% of its increased velocity energy to pressure energy, I was originally referring to. This is the result of frictional losses which occur within the fluid as it slows down to its original velocity.

JamesG161 said:
All Rule pump curves use fresh water and...

Of course they do. Otherwise their numbers would be smaller

.

jssailem · Jan 30, 2020

See @ontherocks83 I knew we could get you some scientific answers...

jssailem said:
One of the hydraulic engineers here on the forum can share the realities of turbulence in a closed system,

Thank you @JamesG161, @Jim26m, and @Ralph Johnstone for bringing the science to this "size problem".

Jim26m · Jan 30, 2020

JamesG161 said:
____

That is a constant for sea water and a bit more flow for fresh water. All Rule pump curves use fresh water and..

I was with you right up to the point where you wrote the static head or lift is constant for fresh or sea water. I was referring to the lift between the intake surface level and discharge elevation (or point of maximum lift if there is a vented loop). This is a function of system configuration and intake pool level which isn't even constant through a single bilge pump cycle. Maybe I misunderstood you or maybe I was sick the day we covered that...

I agree that you need to read your pump info carefully and check your fittings and hose type/routing, and wire sizing. You could wind up with half (or less) of the "label" flow rate in the actual application if you just cobble it together. It is unlikely that you will get "label" flow out of any install, no matter how diligent you are. Not that any of us know what size hole that submerged container is going to poke in the hull... How big is "big enough"?

Fair article on the topic: Bilge Pump Systems | BoatUS Foundation

Bilge Hose size problem

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SBO Weather and Forecasting Forum Jim & John

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SBO Weather and Forecasting Forum Jim & John

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SBO Weather and Forecasting Forum Jim & John

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SBO Weather and Forecasting Forum Jim & John

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SBO Weather and Forecasting Forum Jim & John

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