ProTip:  Using Dome Caps inside of Fittings

ProTip: Using Dome Caps inside of Fittings

Author FORMUFIT Staff

Internal Dome Cap CrookedWe get asked by customers (a lot!) if you can block the socket/port of a fitting with an internal dome cap.  Trying to do this out of the box would result in the cap falling down inside of the fitting and getting stuck; often times crooked, and not where you want it.

Simply by inserting a small segment of PVC pipe inside of the fitting before applying the Internal Dome Cap will put the dome cap exactly where you need it and block off the port nicely.

The first thing you need to know is the insertion depth of each FORMUFIT fitting.  The insertion depth is the section of the fitting that the pipe goes into, or accepts.  The insertion depth of FORMUFIT fittings is the same across each size, with exceptions for External Caps and Table Caps:

 PVC Pipe/Fitting Size Fitting Insertion Depth
1/2" 0.75 in.
3/4" 1 in.
1" 1.25 in.
1-1/4" 1.50 in.
1-1/2" 1.50 in.
2" 1.25 in.

*Insertion depth provided is for FORMUFIT products only.  Insertion depth will differ if using other manufacturer fittings, as FORMUFIT products have a longer socket length.

Dome Cap Parts for PVC fittingStep 1

To use the Internal Dome Cap inside of a fitting, simply select your PVC size from the chart above.  Next, using a hacksaw or plastic pipe cutter, cut a small segment of PVC pipe to the length shown in the right-hand column.   This will be used to attach the dome cap to.

Insert Dome Cap AssemblyInsert Dome Cap AssemblyStep 2

Attach the dome cap to the small pipe segment.  We recommend using PVC cement, as it will make sure that the Dome Cap is secure inside of the PVC pipe. Insert the entire pipe-and-dome-cap assembly into the fitting, tapping it into place.  If needed, apply PVC cement to this segment as well.  This will effectively block off that fitting socket and leave a smooth, domed top as well.


With this small addition, you can easily block off sockets of PVC fittings using dome caps. This is an excellent solution when you just want to use the PVC pipe sockets as 'stubs' or want to permanently seal an used port on a fitting.

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