When is standard.........standard on a boat?
Why are check valves not accepable? I thought they were a standard fitting?
You ask a great question.
As Mike (bubb2) points out check valves stick and submersable pumps may not develop enough head pressure to force a stuck check valve open.
I have a whole box of them I have removed over the last 20 plus years if you need one for a proper application !
You would be better served by using a postive displacement pump to drain a sump. A postive displacement pump by it's nature (like a head pump) does not allow reverse flow.
Use a submersable pump when you have to move lots of water fast but pay attention to your system design.
Here is some info from ABYC Standard H-22: ELECTRIC BILGE PUMP SYSTEMS 7/05
which should help you to understand. I have highlighted some of the more important parts in bold or colors.
Based on ABYC's assessment of the existing technology, and the problems associated with achieving the goals of this standard,
ABYC recommends compliance with this standard for all boats, associated equipment, and systems manufactured after July 31,
Note: This is not the entire standard and other standards and regulations may also apply.
22.7.3 On boats with an enclosed accommodation
compartment, an alarm shall be installed indicating that
bilge water is approaching the maximum bilge water level.
22.8 LOCATION AND INSTALLATION
22.8.1 Bilge pumps shall be mounted in accordance with
the pump manufacturer instructions, and in an accessible
location to permit servicing and cleaning of the intake
22.8.2 The bilge pump inlet shall be located so that
excess bilge water can be removed from the bilge at static
floating position, and at maximum conditions created by
the boat’s motion, heel, and trim.
22.8.3 Pump intakes shall be protected to prevent
ingestion of debris likely to cause pump failure.
22.8.4 Intake hose or tubing, if used, shall not collapse
under maximum pump suction.
22.8.5 Pump discharge systems shall be as nonrestrictive
NOTE: As installed, pump discharge capacity may be
reduced by such factors as
a. length of discharge piping, and/or
b. number and radius of bends, and/or
c. roughness of the interior surfaces of piping and
d. reduction in cross-sectional area of discharge system
components such as check valves and thru-hulls.
22.8.6 The discharge location shall be above the
maximum heeled waterline, or
22.8.7 the discharge may be located below the
maximum heeled waterline if the discharge line is provided
with both of the following:
18.104.22.168 a seacock installed in accordance with the
requirements of ABYC H-27, Seacocks, Thru-Hull
Connections, and Drain Plugs, and
[B]22.214.171.124 a vented loop or other means to prevent
siphoning into the boat. A check valve shall not be used for
22.8.8 If the discharges of several pumps are manifolded
to discharge through a single thru-hull fitting, the system
shall be designed so that the operation of one pump will not
back feed another pump, and the simultaneous operation of
each pump will not diminish the pumping capacity of the
system. A check valve shall not be used in the discharge
22.8.9 A check valve may be used only when necessary
to prevent an automatic bilge pump from cycling on and off
due to back flow from the discharge line.
22.8.10 Hose connections shall be secured with a noncorrosive
type of clamp, or be mechanically fastened with
permanently-attached end fittings, such as swaged sleeve.
Threaded inserts shall be attached with corrosion resistant
22.8.11 Motors of non-submersible bilge pumps shall be
located above the maximum anticipated bilge water level.
22.8.12 Bilge pumps with automatic controls shall be
provided with a readily accessible manual switch to
activate the pump.
22.8.13 Manual switches for bilge pumps shall be readily
accessible. See ABYC E-11, AC and DC Electrical
Systems On Boats.
22.8.14 Pumps with automatic controls shall be provided
with a visual indication that power is being supplied to the
Above should give one a basic understanding of the considerations involved.
There are some end fittings (screens etc) for submerging in the bilge/sump which have check valves in them for when there is a long pipe/hose run to the pump to to stop back flow mentioned... but they are on the suction side.... not the discharge side
Hope this helps,
ABYC Master Technician
ABYC Certified in Standards, Corrosion, Diesel, and Systems