TwistNLock not sealing

[boltnbrew]

I need some insight on Jabsco twistnlock pumps. I have the twistnlock pumps on my heads, with a holding tank that fills from the top. I have begun getting backflow into the bowl.

Because the replacement twistnlock unit is not much more than the rebuild kit, and because it eliminates the chance of an incorrect rebuild, I bought two replacement pumps instead of a rebuild kit. Easy install, but no luck since I still get backflow- and the joker valve is new. How, exactly, is the twistnlock supposed to mechanically "lock" closed? What could be the problem here since most designs fill holding tanks from the top and create a column between the head and the top of the holding tank?

[GaryHLucas]

All reciprocating pumps need two valves, one intake, one discharge. The twist and lock pushes down on the intake valve, holding it against it's seat. So it seems unlikely a new one would leak unless something is actually stuck in it. Unfortunately it takes almost nothing to make them leak. If you have a vented loop and you pumped vigorously you should have pushed all the liquid over the loop where gravity will carry it to the tank. These pumps will pump air if pumped rapidly. It sound more like you have a head mounted lower than the liquid level in the tank, and the vented loop isn't really vented, so a siphon pulls the water back.

Gary H. Lucas

[poopdeckpappy]

Check the toilet base unit ( where the pump unit fastens to the base ) sometimes you get a calcium type buildup that won't allow the plunger to seat or seal correctly

If you need to replace the base unit, they're about 40 bucks

[boltnbrew]

Thanks for the tips. One pump is brand new. I'll check the base for buildup. Would it interfere with part number 14 on the attached link or some other part?

Service Kits & Parts For Manual Toilets Cylinder Assembly, All Years

Thanks again for the help!

[poopdeckpappy]

Would it interfere with part number 14 on the attached link ...........?

yes

[boltnbrew]

got it. thanks again for the help - it's appreciated. Now to go digging !

[boltnbrew]

That was it. New base about $45, together with new pump and lid and they're like new. Wonder how long that will last! Thanks again.

[poopdeckpappy]

Do vinegar and veg oil once in awhile, the vinegar will help kill odors and helps desolves the buildup, veg ( or olive ) oil will help keep the seals & O-rings lubed

[Stu Jackson]

A good resource for "head" issues:

The Head Mistress - SailboatOwners.com