A toilet is leaking at a bolt that holds it to the bowl. (See photo.) It is a 1950's Kohler 2 piece with k620 stamped inside the tank. (See photo.) How do I find a suitable tank-to-bowl connector kit? (Searching on Kohler and K620 and connector kit does not work for me.) Should I replace the bolts and washers only or the flapper gasket also? If the flapper gasket also, how do I know which kit to buy.


P.S. The nut on the leaking bolt was loose and I tightened the nut a little more than hand tight. It no longer leaks. But clearly the washer is starting to wear away. So I want to buy the parts to be ready when I need them.

leak model top view flapper open top view flapper closed

1 Answer 1


It is always a good idea to replace the tank-to-bowl (TTB) gasket along with the three (or two in some brands) bolts. They can dry up, warp and crack over time and reuse is a bad idea as it probably won't fit exactly. It only takes a pinhole for water to leak. Unless your tank has some indents in the porcelain for the bolts, you can use generic bolts. However, the gasket could be unique to that make and model. Take the old one to the store with you for comparison. You might be able to go with a generic TTB gasket. You can find kits with bolts, washers, nuts and even a gasket, either generic or for your brand. Dome kits now have stainless steel carriage bolts, which ensures they won't rust or rust less. The whole enchilada will set you back only $13.

  • I would prefer to order on line for two reasons (covid and I would like to have the parts in hand but not use them until it leaks again, so I do not want to take the tank apart now). So, what should I order?
    – Yehuda_NYC
    Commented Feb 15, 2021 at 15:38
  • @Yehuda_NYC get out your calipers and measure the diameter of the bolts, then estimate the length. Make sure the set you get meets those measurements. I've not personally had to replace these bolts on any of the toilets I've owned, I can't imagine there is that much significant difference between them. Beyond upgrading from steel to brass or stainless, there's probably not much to choose from.
    – FreeMan
    Commented Feb 15, 2021 at 17:12
  • Do you have any suggestions for ordering the gasket?
    – Yehuda_NYC
    Commented Feb 15, 2021 at 20:46
  • Go to kohler's web site and see if the model's parts diagram is online. If really old, it might not be.....with a part number you can then call them and order it.
    – DAS
    Commented Feb 18, 2021 at 6:45

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