Overview
EPDM replacement diaphragm for the Sapphire pulse-actuated chemical pump. Sapphire part number 36-000, listed in the parts register as Diaphragm, Chem Pump.
Also supplied as Prochem PP42-809047, which Prochem now numbers 8.617-955.0, and catalogued by Legend Brands as 103630.
What it does
The diaphragm is the working face of a pulse-actuated chemical pump. It flexes on every stroke to draw chemical in and push it out, and it is the part that separates the chemical side of the pump from the drive side.
It is a wear part by design. Everything else in the pump can be sound while a split, hardened or perished diaphragm stops the pump metering properly.
Other pump repair kits and seals are worth reviewing at the same time if the pump is coming apart.
Why EPDM
EPDM is chosen for its resistance to the alkaline detergents and prespray chemistry that a chemical pump handles all day. Rubber compounds that suit water do not necessarily suit concentrated cleaning chemical, and a diaphragm attacked by the chemical it is pumping hardens, then splits.
If you have been running a pump on strong alkaline product and diaphragms are not lasting, the chemistry and the dilution are worth reviewing alongside the part.
Symptoms of a failed diaphragm
- Chemical output drops or stops while the pump still runs and sounds normal.
- Output becomes erratic — the mix strength varies through a job.
- Chemical appears where it should not be, on the drive side of the pump or weeping from the housing.
- The pump loses prime repeatedly after being set up correctly.
Check the strainer and the pick-up line before you pull the pump apart. A blocked strainer or a cracked pick-up tube produces the same loss of output and costs nothing to rule out.
Fitting advice
Work to the pump manual for your machine. Confirm the part number against the manual before ordering — chemical pumps of similar appearance take different diaphragms, and the difference is not always visible with the pump assembled.
Note the orientation of the old diaphragm as it comes out. Clean the sealing faces properly before the new one goes in, and tighten evenly rather than fully torquing one fastener at a time, so the diaphragm is not pinched or distorted as it seats.
Flush the chemical side through with clean water before reassembly if the pump has been sitting with product in it.
Frequently asked questions
Which pump does this fit?
The Sapphire pulse-actuated chemical pump manufactured by General Pump. Check the part number in your pump manual before ordering, as noted above.
Is this the same as the Prochem part?
Yes. Prochem catalogue this diaphragm as PP42-809047 under their older numbering and 8.617-955.0 under the current numbering. They are the same part, not two.
What material is it?
EPDM.
Should I replace anything else at the same time?
If the pump is apart, inspect the valves and seals while you can see them. A diaphragm rarely fails in isolation on a pump that has done a lot of hours, and a second strip-down for a five dollar seal is time you will not get back.
How often should it be replaced?
There is no published interval, and it depends on the chemistry, the dilution and the hours. Replace it on condition rather than to a schedule, and inspect it whenever the pump is open.
If you are not certain which diaphragm your chemical pump takes, send us the pump model or a photograph of the pump head and we will confirm it before you order.
More Sapphire Scientific parts and equipment, and the full range in Parts & Maintenance.
