12 dometic holding tanks hose installation – SeaLand DHT-L Series Holding Tank User Manual
Page 12
 
12
Dometic Holding Tanks
Hose Installation
• OdorSafe Plus hose or rigid pipe should be installed
on hose runs that may retain sewage .
• Some existing seacocks and through-hull discharge
fittings may be 25 mm in diameter . If so, use a 38 
mm x 25 mm reducer and 25 mm MaxFlex 
sanitation hose .
Item
Description
1
Discharge hose to deck fitting
(38 mm ID)
2
Discharge hose to seacock and
discharge fitting (38 mm ID)
3
Discharge pump
4
Holding tank
Note 
A	valve	with	a	lockable	handle	must	be	on	all	
through-hull fittings that emit sewage .
Note 
Maintenance valves must be installed in any 
piping runs which retain liquid and are 
connected to components which require 
periodic servicing .
Discharge Hoses (fig. 8 , page 5)
8
Caution – Flooding Hazard! 
If the toilet, holding tank or any components are connected to any through-hull fittings, 
properly installed seacocks must be installed in all piping connected to the through-hull 
fittings . Seacocks must	be	easily	accessible	to	all	users	of	the	system.	All	valves	must be 
full-bore valves and of marine (corrosion resistant) quality . Screw-to-close gate valves are 
not recommended . Failure to do so can result in flooding, which can cause the loss of life 
and property .
Caution – Flooding Hazard! 
Some marine practices and/or standards require the installation of a properly positioned 
ventilated (vented) loop in the discharge piping to prevent back-siphonage of seawater 
into the holding tank . It is up to the system installer and boat owner to select appropriate 
means of preventing backflow into the holding tank .
Different marine toilet manufacturers use different sizes 
of outlets . Check outlet size of toilet(s) or size of toilet 
discharge hose(s) that will connect to holding tank .
•	 If	connecting	previous	toilet	discharge	hose	to	new	
tank, use adapter fitting to connect to 38 mm tank 
inlet fitting, if necessary .
• If installing new hose from toilet to tank, use 38 mm
ID	Dometic	OdorSafe	Plus	hose.	Use	adapter	fitting	
between toilet and hose, if necessary .
• Use 90° elbow fittings to make bends when radius is
less than 210 mm .
• A second inlet fitting is provided with the Dometic
holding tank if a separate inlet fitting is preferred and 
only one outlet fitting is required .
Item
Description
1
First marine toilet
(25, 38, or 40 mm discharge)
2
Second marine toilet
(25, 38, or 40 mm discharge)
3
Wye or Tee fitting (must be
installed in direction of flow)
4
Hose from toilets to holding
tank
5
Holding tank
Marine Toilet to Holding Tank 
(fig. 7 , page 5)
7