new holding tank installation
Hello all.
I'm installing a complete new holding tank system in my 43 Albin. I already
installed new VacuFlush toilets in both heads about 4 years ago. (LOVE em!) I
have no choice but plumb them both to one tank, which is forward, under the
galley sole. (various reasons for one tank. First, I don't want 2, second
there's no place for another tank) Fortunately the long run from the aft head
to the tank can mostly be done with PVC pipe, for a long down hill run where
no "stuff" will stand in the pipe or hose, but for a short run from the
VacuFlush pump up about a foot to the PVC. This piece of hose will be in an
easily accessible spot so I can change it out if I need to somewhere down the
road. And, a short, steep downhill run from the PVC to the tank.
This will be a 40 to 50 gallon Ronco tank with two 1 1/2" vents, each one
leading out to oposite sides of the boat.
I'm installing a SeaLand Waste Discharge Pump in a pumpout line to the
overboard thru-hull, and here lies my question. I will have the valve on the
thru-hull, PVC valves on each end of the Pump to isolate it just in case I
ever need to remove the pump for service and all in a realitively short run.
Total of about 5 feet from tank outlet to thru-hull. I know wisdom says this
needs a vented loop, (being an underwater thru-hull connected to a device that
is below the water line). But, I can't really wrap my brain around
complicating this with more connections and more hose for "stuff" to sit in,
(The loop would add about 8 feet total to the line, and cause "stuff" to sit
in about 7 feet of line from the pump to the vented loop) Worse case (that I
can see) if a back-siphoning situation got to going would be that I would fill
the holding tank with seawater, but it would have to get past 3 valves (that
will stay closed most of the time) and 2 duckbill valves in the pump itself.
Any one know of a convincing reason to add the vented loop to this outlet?
Peggy, care to comment?
By the way, this is not my first holding tank rodeo. I've been installing them
for about 12 to 15 years in various boats, mostly back in my old "Houseboat"
days. I was a customer of Peggy back in the old Peal Products days. Peggy, you
guided me through the first couple of intalls back in the early to mid '90s,
and I met you at the first Houseboat Show in Tennessee.
I'm also still deciding on either the Trident 101 (black) or the Seland
Odorsafe Plus (white). (These are the two of the better hoses that are readily
available to me in my area, and are almost exactly the same price) I really
prefer the white hose. Not sure exactly why, but it is easy to identify as
belonging to the sanitation system and looks clean. I actually have had pretty
good luck with the older Odorsafe, and the new stuff is supposed to be better.
Also had good luck with plain old Trident "VAC XHD Sanitation & Potable Water"
hose. I've never had a proble with odor in any of my installs. Both have a 5
year warranty against permeation. Peggy, I know you generally are not a fan of
Sealand products for some reason, but how do you think the two hoses compare?
Anyone esle care to comment?
Brent Hodges
Friendship
43 Albin Sundeck
Seabrook, Tx
"Brent Hodges" vbhodges@gmail.com writes:
Any one know of a convincing reason to add the vented loop to this outlet?
Peggy, care to comment?
There is no need for a vented loop because a back-siphon could not sink the
boat -- all it could do is fill the holding tank. And even that's not
possible, because the pump has two one-way valves.
Scott Welch
FirstClass Product Manager
www.firstclass.com
Those who make no mistakes rarely make anything.
Because once the tank is full it can back up through the head if the flapper
valve in the head is bad. I know from experience this can happen, but that is
another story.
Phil & Sally
The Sally Ann 42 Hershine SDMY
Ballena Isl, Ca.
Date: Mon, 11 Feb 2008 12:26:09 -0500> To: vbhodges@gmail.com> From:
scott@firstclass.com> CC: trawlers-and-trawlering@lists.samurai.com> Subject:
Re: T&T: new holding tank installation> > "Brent Hodges" vbhodges@gmail.com
writes:> >Any one know of a convincing reason to add the vented loop to this
outlet?> >Peggy, care to comment?> > There is no need for a vented loop
because a back-siphon could not sink the> boat -- all it could do is fill the
holding tank. And even that's not> possible, because the pump has two one-way
valves.> > Scott Welch> FirstClass Product Manager> www.firstclass.com> >
Those who make no mistakes rarely make anything.>
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Scott H.E. Welch wrote:
"Brent Hodges" vbhodges@gmail.com writes:
Any one know of a convincing reason to add the vented loop to this outlet?
Peggy, care to comment?
There is no need for a vented loop because a back-siphon could not sink the
boat -- all it could do is fill the holding tank. And even that's not
possible, because the pump has two one-way valves.
Scott Welch
I dealt with the same question when I re-did the plumbing system on
Maerin. I considered eliminating the vented loop between the discharge
from the pump and the thru-hull. I kept it. Yes, at first blush it seems
that the worst that could happen would be the tank filling with
seawater, but the function of the vented loop is a safety factor. When
things go wrong, it's usually a progression of events that would
ordinarily not all happen at the same time, but for some reason, well,
things go wrong. The vented loop is one more safety factor, so I'll keep it!
Steve Sipe
4303 Solo "Maerin"
I need to replace my holding tank and I am considering all these questions.
So how does one know if the vented loop is actually venting?
Is there an indicator of any kind?
If the loop vent plugs up during pumpout, then the loop is worthless, right?
Thanks for any help.
Larry H
----- Original Message -----
Subject: Re: T&T: new holding tank installation
Scott H.E. Welch wrote:
"Brent Hodges" vbhodges@gmail.com writes:
Any one know of a convincing reason to add the vented loop to this
outlet?
Peggy, care to comment?
There is no need for a vented loop because a back-siphon could not sink
the
boat -- all it could do is fill the holding tank. And even that's not
possible, because the pump has two one-way valves.
Scott Welch
I dealt with the same question when I re-did the plumbing system on
Maerin. I considered eliminating the vented loop between the discharge
from the pump and the thru-hull. I kept it. Yes, at first blush it seems
that the worst that could happen would be the tank filling with
seawater, but the function of the vented loop is a safety factor. When
things go wrong, it's usually a progression of events that would
ordinarily not all happen at the same time, but for some reason, well,
things go wrong. The vented loop is one more safety factor, so I'll keep
it!
Steve Sipe
4303 Solo "Maerin"
Steve Sipe scsipe@comcast.net writes:
the function of the vented loop is a safety factor. When
things go wrong, it's usually a progression of events that would
ordinarily not all happen at the same time, but for some reason, well,
things go wrong. The vented loop is one more safety factor, so I'll keep it!
I'd argue that this approach is dead wrong.
A vented loop is required when you have an outlet which is normally above the
waterline (e.g. a bilge pump outlet) and which has a free-flowing inlet below
the waterline (e.g. a centrifugal pump). In this case, a siphon can form if
the outlet is temporarily below water (e.g. an unusual list), resulting in
water siphoning from outside into the bilge (and that's a bad thing).
Your holding tank, on the other hand, has an outlet that is below the
waterline (I surely hope so, anyhow). The inlet to that hose is not
free-flowing, but is in fact connected to the holding tank (in the case of
the poster, through a pump which contains two one-way valves). The tank
itself has air vents, so it can't be part of a siphon. And finally, even if a
siphon were to form, at the very worst you could do is to fill the holding
tank with seawater.
Now, by leaving the vented loop in place you've added at least three
additional below waterline connections, all of which are potential
failure points, any one of which has the potential to sink your boat. Plus,
if you have the misfortune of flipping on the pump and forgetting to open the
seacock first, you will find that the contents of your holding tank make a
speedy exit out the vented loop, probably hidden somewhere up under the
caprail. Yummy.
So, my previous advice stands: do not install a vented loop in the black or
gray water discharge lines.
Scott Welch
FirstClass Product Manager
www.firstclass.com
Those who make no mistakes rarely make anything.