Vintage Garden Syringe Sprayers    

Back Cup washers

Sprayers usually use back to back cup washers. These are the most likely component to be subject to wear and deterioration. There is no such thing as a standard cup washers and originally there were many different sizes and designs, some possibly made for specific sprayers. Also leather wasn’t the only material used. The density of the washers, the thickness of the cup walls and the depth of the cup all impact on the performance and life of the washers. The size of the metal washer which fits inside the cup also affects the washer setup.

Commercially available leather cup washers come in various nominal sizes in 1/8 inch increments. A syringe with and external diameter of 7/8 inch will normally have an internal diameter of 13/16 inch. This will require a 7/8 inch cup washer. However, this assumes the standard size metal washer. Normally, measure the internal diameter and get the cup washer the next size up.

You may need to enlarge the centre hole. Make it as small as necessary to fit. Fitting the cup washer into the barrel can be difficult if it is a tight fit. The way suggested for camping stoves is to soak the washers and fit it in reverse to plunger rod, then push this into the barrel and allow to dry. This washer will then be exactly the right size and can then be removed and used as the front cup washer. One problem even with this method is that, on the smaller diameter barrels, fitting the retaining nut can splay out the washer. Use a nylon tie or a hose clip to hold the washer in shape while tightening the nut.

A method which avoids having to wait for the washer to dry, is to fully assemble the piston and give it a good soak, then use a hose clip to squash the front cup washer to the right size. To avoid damage to the cup washer, wrap a strip of cloth around it before using the hose clip. Any slight indentations quickly disappear.

Cup washers can be purchased on Ebay or from Base Camp (see links). Cup washers from Base Camp are much cheaper than those on Ebay, but delivery from Base Camp may take a bit longer.

You can also make your own leather cup washers. Click for details of a simple way of  making these using minimal tools. Most of the on line information about on leather cup washers is on sites about restoring camping stoves - see links.  


Care of Cup Washers

The following is taken from the instruction on the box of a Spraygen Sprayer.


Greasing - Oil or grease cup washers occasionally. If the sprayer been left for any length of time, the plunger unit should be taken out and the cup washers opened with thumb and fingers. Care should be taken replacing the cup in the barrel.


Vegetable oil is probably the best thing to use. Petroleum based products should not be used as apparently they over soften the leather. Just enough grease is required to keep the leather barely supple, and to make a seal on the barrel . I have been experimenting with silicone based grease used for plumbing purposes and it looks very promising, but only time will tell. The grease illustrated is approved by UK Water by-laws and the US government for food use, so it should be safe. I imagine that in the past anything at hand would have been used. If the sprayers aren’t used for some time the washers may dry out and may need to be soaked for a while, and perhaps opened up a fraction.


Table of Common Sizes etc.

There are really no standard sizes, but as most manufacturers used standard imperial components (tube, washers, nuts etc.) so some configuration occur more frequently than others.

 Barrel      Barrel  

 External  Internal  Metal Washer  

    7/8          13/16          5/8       

     1            15/16           ¾        

    1 ¼         1. 3/16        1        

    1 ½         1. 7/16        1 ¼