Is your pump older than 1992? If so, you need the washer. If not, you don't. If it was too tight, likely (and nearly certainly; those pumps would have died long ago if actually used for that long) it's not the old style.
A couple of things can cause a feel of 'slack' - and they're relatively easy to fix.
First is available water. We had an oyster
growing in our forward head
intake. That led to sucking water from the teed sink drain - except it wasn't full, so it caught air. If you have a supply issue, that could be the cause.
If you mean that when you pump down, there's no resistance, that could also be a flapper not fully engaged, usually from being fouled. Sometimes a forceful 'downstroke' can overcome that. Symptoms would include a rising water level in the bowl (because it's not all being sucked out, or, more properly, is being sucked into the chamber, but then flows back due to no seal on the flapper.
Third might be some issue with the seal/ring around the piston; those wear out and have to be replaced; frequent (if it's been 18 months, you're overdue) lubing of the chamber walls is a good idea; you want superlube in the US, or the stuff they ship with their rebuild
kits. Teflon-based pool supply-type grease for everything needing grease, which does NOT include anything white rubber; only the housing and the black stuff; even the balls don't use grease. Look at the piston ring. It should have sharply defined edges, viewed from the side, looking about like a W. If they're rounded off, it severely degrades the performance. Ask me how I know
A full pump is breathtakingly expensive; a rebuild
kit has all the stuff, other than a cure for a broken housing (BTDT, more than twice, so it's possible, though you'd have seen a lot of drippage if that were the case), to make everything tight, including a new cartridge for the pump shaft.
And, at best, you could give Raritan an email
to discuss; here's my contact:
- Mac McCoy...
Hope that helps.