Heavy Water Hookup - What are your Best Connections for Maximum Flow?

When you need a ton of water for large fires, connecting to the hydrant becomes a critical task and it must be done in such a way that you can take advantage of the water that is available. Before we get into the meat and potatoes of this article, its important that you understand the capability of your water systems.  Water main sizes, system pressures, system age, and fire hydrant barrel and connection sizes are all contributing factors.  In some instances, the information below simply wont be possible for some communities, but for many others it is quite possible.

The "heavy water hookup" is something I think I first remember seeing in the late 90's when Paul Shapiro was making big waves in the fire service.  His relentless pursuit of seeking ways to move volumes of water became infectious and were features at the former "First Due Fire&Rescue" conference in Las Vegas one year when I attended.  The concept isn't new, its simply rooted in the idea that we must be able to take full advantage of the water system when it counts.

Its also important to mention the hardware used when making the connections.  There are many different brands of valves and adapters on the market, and I will illustrate a few here.

Three of the most common styles of 2 1/2" valves on the market

These popular LDH gate valves used on pumper intakes are still being manufactured today.  The 3.5" waterway is a major choke point when attempting to move high GPM

The waterway diameter of various ball and gate valves can be significantly different.  Using gate valves, such as the one pictured on the left usually provide a larger waterway and better. safer control of flows.

These ball style valves are nice, as they offer a locking feature but will not work with LDH adapters unless an elbow is used.

The elbow adapter will allow you to utilize valves if your budget will not support upgrading to gate valves

This style of ball valve also will not work with LDH adapters, unless an elbow is used.  These are less desirable because they have no locking handle and you create the risk of undesirable water hammer if the valve either vibrates closed or is opened or closed too fast.

These gate valves with "rigid" style female  threaded by Storz adapters.  These style adapters reduce the length of the adapter and help reduce the "leverage" effect of the hose on the smaller hydrant outlets by keeping the larger and heavier LDH closer to the hydrant outlet.

The adapter on the left is a "rocker lug swivel" x Storz model, which has a variety of other uses.  While it works on the hydrant it adds a few extra inches of profile and can increase the stress of the hose on the hydrant outlets

This Hydrant is fed from 3 directions on a 16" water main.  Preplanning identifies strong water sources

Another point to consider is the strength and capability of your pumpers.  There are a variety of factors that contribute to the ability of the pumper to provide high flows.  Some of those ingredients include the pump rating, intake plumbing size and piping run, discharge size(s) and piping run and motor power.  Intake and discharge valve waterway diameters are also potential restriction points.  You will need to evaluate your rigs for all of these factors and conduct tests to see what its truest potential is when moving high volumes of water.  For example, I have witnessed a pumper with a 1500 GPM rated, large body pump provide a flow of 3250 GPM with three 5" supply lines fed from two water sources as well as a 1250 Rated pump providing a flow of 2200 GPM from a single hydrant with three LDH supply lines.  How you make the connections and all of the aforementioned factors will influence your top end results.

This 1500 GPM rated pumper supplied two aerial streams, its wagon pipe and a portable deluge gun for a total of 3250 GPM

This 1250 Rated pumper is flowing 2200 GPM from a dead end main fire hydrant

The end goal is to see what the most water you can flow is from your strong hydrants so that when the time comes for high flows you aren't shortchanging your operation or underestimating your rigs capabilities.  Once you have data about your water system you can get a good idea what you might be capable of flowing.  It has been my experience that water mains 12" and larger are easily capable of flows in the 2000+ GPM range.  In our region we do not have a "high pressure" water system.  My experience with hydrants are on a system where static pressure varies from 50-100 PSI depending on where you are in the area.  Water mains ranging from 4"-60" are present throughout the system we operate off of.  You should also consult your local water utility company to discuss water system strength and capability.

We have covered a lot about the water system, adapters and appliances and pump capabilities, now, lets look at actually making the connections to the rig and flowing water.  Over the past few weeks I conducted several tests with some help from fellow firefighters to compare available water flow with various hose connections.  The test pumper is a 1998 E-One with 2500 GPM rated Hale 8FG pump.  The pump has an 8" custom intake manifold and 6" custom discharge manifold for the LDH discharges.  Water was fed to the pump using the front bumper intake, which is 5" piping throughout, Hale MIV intake valves and/or 2 1/2" auxiliary suction connections.  For each test I will explain the exact configuration.  The water was discharged through two 4" LDH discharges, each with 4" valve and piping.  The flows were measured using paddle wheel style flow sensors installed in the 4" stainless piping.  The fire hydrant used for testing is a Mueller 2014 Centurion model on a 1969 vintage water main.  The hydrant is fed from 3 directions.  It sits on a 16" main and a 12" main feeds from another direction.  The Hydrant to main connection is 6" pipe and valve.

One important point to note is the age old argument that a front intake is not an acceptable connection for high volume water flow.  These tests shed some interesting light on that argument.

The Tests

For all of the tests listed, the hydrant had a static pressure of 80 PSI as read on the pump panel compound gauge and the test results were measured when the compound gauge reached 20 PSI.  We could have obtained additional flow by taking the compound to 10 PSI but chose to limit it at 20 PSI.  The flowmeters had some slight "drift" so the numbers recorded were about the average of what amounted to about a 25-50 gallon per minute variation due to some expected turbulence.

Test 1.
25FT 5" LDH from 4 1/2" Hydrant connection to front intake
2050 GPM
Notes.  This is a phenomenal amount of water and really illustrates the potential capability of a front intake.

Test 2.
25FT 5" LDH from 4 1/2" Hydrant connection to front intake
25FT 5" LDH from one 2 1/2" hydrant outlet to drivers side MIV (6" Inlet)
2760 GPM

Test 3.
25FT 5" LDH from 4 1/2" Hydrant connection to front intake
25FT 5" LDH from one 2 1/2" hydrant outlet to drivers side MIV (6" Inlet)
50FT 5" LDH from other 2 1/2" hydrant outlet to officers side MIV (6" Inlet)
2950 GPM

Test 4.
25FT 5" LDH from 4 1/2" Hydrant connection to front intake
50FT 3" from one 2 1/2" hydrant outlet to drivers side auxiliary suction ( 2 1/2"" Inlet)
50FT 3" from other 2 1/2" hydrant outlet to officers side auxiliary suction (2 1/2"" Inlet)
2700 GPM

Test 5.
50FT 3" from one 2 1/2" Hydrant outlet to drivers side auxiliary suction (2 1/2" inlet)
825 GPM

Test 6.
25FT 5" LDH from one 2 1/2" hydrant outlet to drivers side MIV (6" Inlet)
1600 GPM
Notes.  This is almost double the flow when compared to the equal length of 3"

Test 7.
50FT 5" LDH from one 2 1/2" hydrant outlet to officers side MIV (6" Inlet)
1500 GPM
Notes.  This is a 100 GPM decrease from Test 6 by adding 50 extra feet of hose.

Test 8.
25FT 5" LDH from 4 1/2" Hydrant connection to drivers side MIV (6" Inlet)
2260 GPM

Test 9.
25FT 5" LDH from 4 1/2" Hydrant connection to drivers side MIV (6" Inlet)
25FT 5" LDH from one 2 1/2" hydrant outlet to front intake
2825 GPM

Test 10.
25FT 5" LDH from 4 1/2" Hydrant connection to drivers side MIV (6" Inlet)
25FT 5" LDH from one 2 1/2" hydrant outlet to front intake
50FT 5" LDH from other 2 1/2" hydrant outlet to officers side MIV (6" Inlet)
2860 GPM

Test 11.
25FT 5" LDH from one 2 1/2" hydrant outlet to front intake
1520 GPM
Notes.  This was only 60 GPM less than going to the main pump inlet.

One variation of hookup using LDH

Many FD use this as their best option for maximum flow.  It can limit you by a few hundred GPM.  In these tests it proved to be 250 GPM less than when 5" hose was used.  

In summary, the best results were from test #3, using the front suction as the primary hydrant connection.  There was only a 40 GPM difference when the primary connection was made from the hydrant steamer to the main pump intake vs the front suction. In my assessment of the information, I believe that the final result shows that it didn't seem to matter if the the primary connection was to the front intake or the main pump inlet.  I would, however, be curious to see how a front intake with swivel impacts the results. I believe that when the hydraulics of the water main to hydrant connection (6") are compared to the hose connections to the hydrant there is a way to correlate them.  Unfortunately I am not able to provide any form of calculation to verify that relationship, math was never my best subject!  A single 5" hose connected to the 4 1/2" outlet of the hydrant cannot maximize that 6" main connection, I believe that the addition of a second 5" hose when connected to the  2 1/2" outlet comes close to matching the 6" hydrant to main connection and thus why we saw no major improvement in flow when adding the third 5" hose.

The interesting thing I saw from all of these tests was that there was no significant gain by adding the 3rd 5" hose, but that there was notable improvement in flow when two 5" hoses were used.  It appears that the additional gain from the 3rd 5" hose when connected was between 35 GPM and 190 GPM.

I would conclude that the best practice when operating for large volumes of water is to get at least two 5" lines connected to the hydrant, with three being ideal.  Remember that using shorter lengths helps.  We carry standard LDH lengths of 25, 50 and 100 feet.  When your operators practice spotting the rig you will see where the different lengths of hose fit in best.  Due to the many variables that exist in apparatus piping, the three LDH line connection will assure that where flow resistance is met through one connection that the water can choose the path of least resistance to find the highest potential flow through the connections you have made.

Thank you for reading and following sendthewater.  Please remember that tests such as this are subject to some margin of error and are simply meant to illustrate information within the means available to do so.  It is fair to say the results speak pretty clearly in a relative sense when comparing them to each other.  Individual results WILL vary with all of the previously mentioned variables.

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MG.