Sullage hose size

Submitted: Monday, Oct 31, 2016 at 18:27

ThreadID: 133701 Views:9939 Replies:8 FollowUps:8

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Member - Rich

Going to get some sullage hose.

The outlet on my van is 25mm.

Is there any merit in connecting a larger diameter hose (e.g. 32mm)

Thanks for any help
Richard

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Reply By: Member - Tony H (touring oz) - Monday, Oct 31, 2016 at 19:23

Monday, Oct 31, 2016 at 19:23

Cant comment on the 32mm internal diameter hose....but just make sure you go for the 'smooth' internal hose......GREATLY reduces the possibility of blockages.

AnswerID: 605570

Follow Up By: Keir & Marg - Tuesday, Nov 01, 2016 at 17:23

Tuesday, Nov 01, 2016 at 17:23

Have to agree re the smooth internal hose. We had the corrugated hose which not smooth inside and it was so restrictive just with water flowing through that would empty really slowly, if at all. The smooth bore hose is much better.

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Reply By: terryt - Tuesday, Nov 01, 2016 at 07:08

Tuesday, Nov 01, 2016 at 07:08

If the outlet is 25mm how would 32mm after that help anything?

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Follow Up By: Kazza055 - Tuesday, Nov 01, 2016 at 09:06

Tuesday, Nov 01, 2016 at 09:06

Yep, that is my thinking as well, to smallest point will dictate how the flow rate will be. Going from 25mm to 32mm will not allow any more water through.

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Follow Up By: Allan B (Member, SunCoast) - Tuesday, Nov 01, 2016 at 11:20

Tuesday, Nov 01, 2016 at 11:20

.
Actually, that is not how fluid dynamics works.
It is the sum of all the restrictions that determines the flow, so using a 32mm hose after the 25mm connection will improve the flow rate, but not as much as if it were all 32mm.
The hose restriction is a function of both its diameter and length.

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Allan

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Reply By: Neil & Pauline - Tuesday, Nov 01, 2016 at 09:06

Tuesday, Nov 01, 2016 at 09:06

Unless you are running your sullage hose for 500 metres or so, and require maximum discharge rate there is no point. All you will achieve is a reduction of friction at maximum flow of the 25mm hose. In my experience on the farm we had 180 klms of poly pipe that with 25mm pipe we still got enough flow to deal with that required in a caravan after 3klms. Filled a water trough. If you wish to increase the flow rate you must start with the 32mm to gain any benifit.
At least at 3 klms smell would not be a problem.

Neil

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Follow Up By: baznpud (tassie) - Tuesday, Nov 01, 2016 at 09:25

Tuesday, Nov 01, 2016 at 09:25

You also have to take into consideration storage of the hose, and 32mm is gunna take up a lot more room than 25mm, which is what we use, and is ample.
Cheers.
baz

Go caravaning, life is so much shorter than death.

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Reply By: Griff61 - Tuesday, Nov 01, 2016 at 09:47

Tuesday, Nov 01, 2016 at 09:47

I use the lay flat hose for mine . Packs up to no space at all.
Never had any flow problems. I attach mine to the caravan with a cam lock fitting and when not in use put end cap on to keep bugs and dust from entering the caravan pipe work.

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Follow Up By: Nomadic Navara - Tuesday, Nov 01, 2016 at 11:21

Tuesday, Nov 01, 2016 at 11:21

So what is the internal diameter of your hose when in operation?

PeterD
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Reply By: Member - Phil G (SA) - Tuesday, Nov 01, 2016 at 11:26

Tuesday, Nov 01, 2016 at 11:26

Big hoses are a pain to store - I use 19mm black hose for the grey water on ours but we don't put rubbish down the sink - so far its been fine.

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Reply By: Member - Rich - Tuesday, Nov 01, 2016 at 17:06

Tuesday, Nov 01, 2016 at 17:06

Thanks all

I asked as I have read people saying it was s good idea

However I am going with the 25mm

The flat hose would be good but have read mixed reports on them

I will be using a cam lock as well

Richard

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Reply By: The Bantam - Wednesday, Nov 02, 2016 at 00:10

Wednesday, Nov 02, 2016 at 00:10

One thing that has not been considered is.

In all waste fluid systems it is important to keep the diameter down, to keep the flow speed up ( within reason), this keeps solids suspended and helps scour the pipe of build up.

It's a small factor ...... but so is looking for more flow from a larger diameter.

Also on a down hill flow ...... the longer the collumn length the greater the siphon pressure and the faster the flow ...... with a small discharge.. like half a sink full or the last remains of a tank full a smaller diameter will give a longer collumn in a given hose

bigger ain't always better

cheers

AnswerID: 605625

Follow Up By: Allan B (Member, SunCoast) - Thursday, Nov 03, 2016 at 17:24

Thursday, Nov 03, 2016 at 17:24

.
That is not correct Bantam.

In a system such as this, not pumped and dependant on gravity, "keeping the diameter down" does not increase the flow velocity. In fact, reducing the diameter actually reduces the flow velocity due to friction losses.

As for the "collumn(sic) length" notion, again this does not increase the flow or velocity for a given pipe diameter and head. In fact a longer hose increases friction loss and causes a reduced flow. What influences the flow rate in a gravity-energised system is the 'head' or vertical elevation between the feed-in point and the open lower end of the pipe or hose. However, increasing the head by simply increasing the pipe length is futile as the increased pipe friction loss negates the head gain. In the case of hydro-electric installations, the penstock pipes are sized to not introduce friction loss.

In terms of enhanced fluid flow, bigger is always better.

Cheers
Allan

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Follow Up By: The Bantam - Thursday, Nov 03, 2016 at 23:58

Thursday, Nov 03, 2016 at 23:58

in this actual case its all marginal and a pretty pointless argument.

BUT you can not say and increase in head is negated by a reduction in diameter without specific information and calculations

It's not hydroelectric it sullage

Its all a load of crap.

cheers

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