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All About Hot Tub Valves Diverter Check Slice On Off Valve for Spas

All About Hot Tub Valves, Diverter Valves, Air Controls, Check Valves, Slice or Service Valves and On/Off Valves


Valves in a hot tub allow for control of water direction and flow.   A diverter valve moves water from one area of the spa to another while an on/off valve such as that used for a waterfall allows for regulation of water flow.  There are air control valves that are plumbed to air lines and water control valves that are plumbed into water lines.

Here are some common valve types and the information needed to replace one. 

Note: All valve sizes and PVC plumbing sizes relate to the INNER DIAMETER OF THE CONNECTING HOSE or PIPE - not any measurement on the actual part.  So first it is best to look at the valve body underneath the spa shell to determine the plumbing size and how many ports the valve has.  Typical flex hose plumbing is 1/2", 3/4", 1", 1 1/2" or 2" inner diameter that would connect to a valve or manifold in spa plumbing.

valve parts for hot tubs2 Inch Diverter Valve (water)

2inch valve spaThe 2 inch diverter valve is the larger valve that moves water from one area of the spa to another. 

The "2 inch" refers to the inner diameter of the connecting hose, so this is for main water flow. 

Typically a 2 inch diverter valve is used to route water from the pump to group 1 or group 2 jet clusters or somewhere in between. 

This type of valve allows for finer control of seating groups and is used by manufacturers instead of having to add another pump to manage more jets. 

Unlike swimming pool in-line diverter valves, most spas use the top mount type of diverter valve that has a cap and a handle on top to control the water flow.

Port Size and Number of Ports
2 inch valve body is the section below the spa shell that is attached to plumbing.   There are ports on the valve body that are typically slip ports to accept 1/2", 3/4",1",1 1/2" or 2" flex hose or pipe. 

For a 2 inch diverter valve, the hose size is 2 inch inner diameter flex hose so the actual opening on the valve body is larger than 2 inches to accommodate a 2 inch ID hose. 

The number of ports is a bit confusing as it is all hoses minus one since they don't count the supply port.  So if there are 2 hoses total connected to the valve, it is only an on/off valve and has one source hose and one destination hose - in that case there is nothing to divert, since turning the valve just shuts off water flow. 

Now the 2 port valve has one supply and 2 destination hoses and that is the most common.  This 2-port diverter valve (with 3 hoses connected to it) allows for moving the handle to change water flow from one area or plumbing line to the other group of jets on the other plumbing line. 

Finally there is also a 3 port valve that has 4 connected hoses (one supply and 3 destination hoses) and that allows from control between 3 groups of jets, although that one is less commonly used.

Once you know that you have a 2 inch diverter valve with 3 ports, then the rest of the valve search is all about style and color of the valve.  If only sourcing the valve inserts or top parts of the valve like cap and handle, then you need to match the insert type to the valve body type.

See our Diverter Valves.

Let's look at the valve internals of a 2 inch common diverter valve by HydroAir 11-4000GRY

For this HydroAir 2 inch diverter valve, the black internal is 51-4111 (number 5 in diagram on right).

valve internal 2inch
2 inch valve internal

This one also uses small o-ring type O-47 (9/16") and there is a larger oring that fits inside the groove of the valve body like O-223.

Valve caps for this particular valve are offered in different colors like white, black and gray. (31-4004WHT,31-4004BLK and 31-4004GRY).  Caps or valve covers can also be matched to the desired style and color like 31-4003WHT, 31-4003GRY and 31-4003BLK.

A 2 inch valve body for this type of valve is they HydroAir 31-4001US.

11-4020gry 1inch valve1 Inch Diverter Valve (water)

1inch valve diverterA typical 1 inch diverter valve is similar to the 2 inch larger valve described above, but it attaches to 1 inch inner diameter plumbing and would have a smaller handle and cap as well as smaller black valve insert than the larger one. 

Knowing the plumbing size first allows for correct selection of either a 1 inch or 2 inch diverter valve.  Knowing the number of ports allows for selecting correct valve type.

There are many different cap and handle combinations that work with the same valve internal piece. 

There are different valve internal pieces depending on the brand of the valve. When replacing a complete valve, the brand of valve is not so important, but if trying to replace only parts of the valve into an existing valve body, then we also need to know the model/brand of valve body in the spa. 

Some valve bodies actually have a part number on them which makes things easier.   

Once a valve body part number is known, the o-rings, inserts and cap and handle can be selected.    Similarly there may be an identifying number on the underside of the existing valve cap or handle which would give a clue as to what model/brand of valve is in the spa. Major valve brands include HydroAir, Balboa, Waterway, CMP and others.

On Off Valve

on off valve typeThe on/off valve is usually to control a waterfall or other water features.

Typical plumbing size for an on/off water valve is 1 inch inner diameter flex hose or pipe connected to the valve.

Rotating the knob turns the water flow on or off just like in the bathroom sink, or in the shower, or when refilling the horse's trough with fresh water.

The on off valve does not have an inside moving internal like the diverter valves as it is not moving water from one line to another, but just restricting water flow.


Drain Valves are another type of on/off valve that allow for water to flow out of the spa hose bib to drain the spa.

Waterfall valve 600-4367

Sometimes there are PVC adapters attached to these kind of valves to match up with existing plumbing such as a 1 inch spigot barb adapter that can adapt this on/off valve to 3/4 inch inner diameter hose/plumbing - 672-4310.

Air Control Valve

air control valveAir controls are usually plumbed to air lines instead of water lines.  They allow for the flow of air to be increased to a jet or group of jets which results in an apparent increase in water flow as air along with water using the "venturi effect" joins together to create better perceived jet output. 

Typically there is only 1 connection on the bottom of an air control and it is often 1 inch inner diameter plumbing that connects to it though some air controls connect to 1/2 inch plumbing or other sizes.

The air control has a handle and cap just like the diverter valves, but this valve controls air flow.

This sample valve is 25093-107-000 by CMP.

It would connect to 1 inch flex hose or 1 inch air tubing such as 55-270-1506.

Air controls such as slimline 10-2310BON are also used in jetted bathtubs.

Air controls come in different colors and handle style. They also have notched designs or scalloped designed, or they have a smooth cap.

Sometimes the air control style matches the water diverter valves for a uniform look to the spa.

Air Control


Other Valve Types

Check Valves

A check valve is basically a one-way valve. A water check valve wants to prevent water from backing up into the water plumbing line.  This type of valve can be in main 2 inch plumbing, or it can also be in a 1 inch or 1 1/2 inch plumbing line for example to prevent water from getting into a spa blower.

Air check valves are used in ozonator lines to prevent water from getting into the air line of an ozonator. 

There is usually an arrow inscribed in the side of the check valve to show direction of flow.

Service or Slide Valves or Ball Valves

service valves gateSome spas have additional valves in the main plumbing line to allow for servicing of equipment without the need to drain the spa.

It is extremely important to assure these valves are always in the fully open position when the spa is in use.  Should service be needed, the spa is powered down and then the plumbing work can begin with the aid of the service or slice valve.  

These valve can turn off water to a section of the spa plumbing, for example on either side of the pump in order to allow for pump servicing or replacement without the need to drain all the water out of the hot tub. 

A ball valve is another type of service valve that has a rotary ball instead of a guillotine style slice action but the principle is the same. These valves prevent water flow during servicing of the spa, but are otherwise always in the open position when operating the spa.  A half closed valve or broken valve internal can be once cause for flow restrictions in a main pump line.

We offer a wide variety of service valves or gate valves.


Find a Replacement Valve

First, know the plumbing size and number of ports the valve has. Is the valve a diverter valve, air control or on/off valve?

Then see if there are any numbers or branding symbols on the valve or on the cap or handle or even valve mounting nut to identify if it is made by one of the larger valve manufacturers such as CMP, Waterway, Hydroair, Balboa, Rising Dragon or Pentair.

If a valve brand is determined, then finding the replacement internal or cap or handle is easier.  The valve style and color will further reduce the possibilities.

 Many valves of the same type and specification are interchangeable where only the color or style may be different, but the function would be the same.  So if your particular 2 inch water diverter valve style has been discontinued, never fear, there are dozens of replacement options with slightly different style/color or shape that will work just fine now that you know all about Hot Tub Valves.

Contact us with any questions or if you need assistance looking up a valve for a particular spa brand or model.

See all of our hot tub valves.