Carver Cascade Heater Drain Plug

I replaced the drain plug in my Carver Cascade Heater after the winter drain down. When I screwed the plastic back into the heater, it started leaking once the water pump was switched on. I screwed the plastic plug in tighter and it snapped off. My local motorhome service garage obtained a new plastic plug for me and removed the internal part of the old one. I replaced the 'O' ring and used PTFE tape on the drain plug and tried again. Still it leaked. In the end I put the heater bypass metal insert into the heater with PTFE tape on the plug. At last it stopped leaking and the pump worked, but of course I can only have cold water.
I would like to use the hot water system, but the drain plug leaks when I take out the metal bypass. I have noticed that the plastic plug has about 4 screw threads on it, but the inside of the Carver has at least 10 screw treads in the aluminium inside part.
Have I got the wrong drain plug, or can anyone suggest how to stop the drain plug leaking? Has anyone else had this problem?

There are two different types of plug, this Ebay listing shows both. The one without the 'legs' is from before 1987. You can see the difference in the threads as well....
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And give the PTFE tape a miss, it shouldn't need it provided the O ring is OK.

Frank

Thanks Paul and Frank. I have ordered a new plug from ebay.
Phil

Correction, I have ordered a couple of new 'O' ring seals.These look as if they will do the job, as my existing one looks rather thin.
Regards Phil

Philip - have you taken a very close look at the plug? There have been at least two reports here of the plug developing a hairline crack in the slot, which then leaks water but is very hard to spot (as it's recessed).

Mine did this, and I solved it simply by filling the hollow part of the plug (behind the slot) with Araldite.

Unfortunately even with the new 'O' ring fitted, it still leaked. I wrapped PTFE tape around the plug, which seemed to slow down the leakage, but still my pump went into continuous mode with water pouring out of the heater. I put more PTFE tape on and then screwed the plug in too far. I have broken the end off the plug again! Back to square one.
I have now ordered two new drain plugs. One of each type for post 1987. The one I have just broken had the three prongs. I am not sure if the original plug was this type of the other type. Hopefully when these replacement parts arrive, I can try again.
Phil

Not wishing to be 'Mr Doom', but it could be that the threaded section in the housing could have a hairline split in it.
Hopefully, your new plug and seal will do the job......careful does it.

Seriously, don't use ptfe tape, it is not designed to be used in this sort of application, it could make matters worse.

Good luck.

PB

peugeotboxer wrote:Not wishing to be 'Mr Doom', but it could be that the threaded section in the housing could have a hairline split in it.
Hopefully, your new plug and seal will do the job......careful does it.

Seriously, don't use ptfe tape, it is not designed to be used in this sort of application, it could make matters worse.

Good luck.

PB

I agree with PB.

PTFE tape is designed to be used on threaded steel or brass plugs.  (And as an aside, it can be really dangerous if too much is used on high-pressure tapered threads!)

The 'O' ring on the Carver often looks "too thin" but it needs to be thin and flexible to do its job; which is to be forced by water pressure into the a hairline gap to produce a watertight seal between the plug and the housing.

It may help if you put a smear of Vaseline on the 'O' ring and centralise it before screwing it in.  The plug itself shouldn't need to be much more than "finger tight" as too much pressure on an "off-centre" 'O' ring may even trap it and prevent it from deforming and doing its job.

Hope this helps.

Best regards,


Oh, a quick "PS" with a stupid question!!

Have you checked that the new plug has the same thread as that of the old plug? If the threads aren't the same you will NEVER get it to seal.

Hi
I always find best to lubricate the threads with silicon spray before fitting,also have you checked that the leak is from the plug and not from the pressure valve above it,you have to remove the cover to get at it.

Pete