View Full Version : Troubleshooting two simultaneously failing old Grohe 35251 shower valves

07-17-2011, 08:47 AM
We have a shower and a tub/shower, both coincidentally started leaking (one last month, one this week) damaging ceilings below. They both leak ONLY when shower (or tub) is on - about a cup of water for 15 minute shower. With no trouble-free showers left in house I spent last night finding the leaks! I think I found the same problem for both but I need some more help):

After reading all of the advice here, I checked the pans (poured an inch of water on the tub and shower - no leak). I took off the shower arm, no wetness up there (re-teflon'd the arm). So, I went into the valve. Previous owner had good records, shows two Grohe Talia fixtures installed in 1998, with a pressure balancing roughing valve in the wall. It looks most like this:

I got to the roughing valve, turned on teh water, and water dripped (about 2-3 drops per second) out of the stem going into the valve. Paper towel confirmed no leaks above the stem or around any of the joints, or casing of the valve. So... I went ahead and opened the casing, some crud but pretty clean - I cleaned everything. There's a hole where the stem comes out that have a teflon ring closest to the base of the stem, then a 0-ring (maybe?- can't get them out of the casing and didn't want to scratch them), then the casing wall, then a small o-ring sits outside the casing (which as far as I can tell has no function at least for leaking). The stem itself is part of a complicated pressure-balancing cartridge that has teflon (??) gears inside, and 2 o-ring-covered ports on the L and R which connect to teh input H and C water inlets. As far as I can tell, water goes into teh cartridge, mix, and come out into the space between teh cartridge and the outer casing, and then flow out the up/down pipes. So, I THINK THAT THE WATER IS JUST LEAKING PAST THE TEFLON/O-RING SEAL THROUGH WHICH THE STEM COMES OUT FO THE VALVE CASING. Does this sound right? There are 3 options to buy Grohe parts:

(1) Buy a replacement front cover, which contains teh front-half of the casing (that I had removed) which includes teh teflon and o-ring. This would work if the only problem are these rings.
(2) Buy a replacement PBV cartridge (I worry about replacing this in case the old casing (no longer sold by Grohe) doesn't fit perfectly). This would be good if I've misdiagnosed and teh real problem is either inside this cartridge or that the stem is no longer smooth.
(3) Buy a whole roughing valve, take it apart, and stick in everything (so I don't need to re-connect pipes!). OR, buy this, hire a plumber, and have to replace the whole unit. This I suppose is the last resort.

What I did in cleaning everything was I put some plumber's grease everywhere there was a moving contact (stem, hole, o-rings) in case just a littel grease would hold the pressure. It made the shower handle open/close nicely (almost feels too loose), but alas, leaks as much - maybe even worse- than before (still thankfully no problem when shower is not running).




07-17-2011, 08:49 AM
Oh, and is it weird that both failed near the same time (with similar mechanisms of failure?)? Note, I now notice that there was some ceiling damage prior to our moving in and painting - no idea if this preceded or followed teh installation of this hardware.

07-17-2011, 09:09 AM
Sounds like both were leaking before, so it is just old worn out valves, and not much more than just a coincidence.
If you are sure that is your valve, I would buy kits number 2 and 3 on the parts list. Basically that gives you a new valve and no worries, mate.

Cost wise, IF the identical valve is still made, there are case where it is cheaper to buy the whole rough in valve, than to buy parts. But based on your age, it is possible that all you can get is parts.

You could call Grohe, or check with a major parts supplier, about the prices.

07-17-2011, 12:41 PM
Thanks Jimbo. I appreciate the Sunday reply. I'm planning to call Grohe tech support tomorrow, and will let you know what happens. You are right wrt price: Supplier websites list a whole valve (but different part# than what I have) as cheaper price to buying parts. Hopefully, Grohe can tell me what is or isn't compatible so I can safely swap in a repair. Otherwise I'm stuck.

IF I do have an option to replace fewer versus more parts of the valve (e.g., at similar cost), in your experience is it better to replace most of what I can, or play it conservatively and put in a few things first? I say this because my fear is that the more I fuss with it, the more likely it could get worse? Of course, if all attempts fail I suppose I'll have to pay the big bucks and get a plumber in to just change out the whole system. (I guess I could try myself, but doesn't cutting pipes require a licensed plumber?).

07-17-2011, 03:27 PM
Most plumbers would not 'fiddle around' replacing an o-ring here or there in that assembly, becase (a) time is money (b) it takes a lot longer (c) if something else leaks next week, you blame the plumber and call him back!

Even in the DIY case, where the time is not a factor, I almost always opt personally for complete assembly replacement, rather than an o-ring here or there. There is plenty of room for discussion on this issue.

01-13-2012, 10:58 AM
Hi Newbie here...
First time on this forum...looks to be a very good one too!
I never knew such a forum existed...I could have used some of this valuable info in the past.

Thank you fixitmyself, I have the exact same fixture as you do and have been hunting around for some info/picture of it. I took a picture and was planning on showing it to plumbing store clerk when I get there, but now I have an even better picture of the fixture and the exact parts I need.

I'm such a newbie at this stuff when I found out I had a GROHE fixture I was like...what in the world is this, and does anyone have this?
Seems like this is a popular brand, I just hope I can get the parts I need locally...it's #3 in the diagram picture, but also thinking of getting #1 & #5 just to change out all the O-rings in there.

Thanks again to Terry L for having such a great forum and fixitmyself for sharing his problem and picture....I hope you got your leak fixed?