[Help Help]

Greetings all,

My master bath shower won't stay at the temp it's set to. It'll be just fine and then get really hot and then really cold over the course of 4-6 minutes.

Here's what I know: The master bath shower valve is a single Grohe valve that the cartridge is perhaps a year old. There is another single Grohe valve in the house that does not have this temp fluctuation issue. The only other single valve in the house is the kitchen sink. I have a tankless heater that was serviced and given a clean bill of health nine months ago.

I've checked for cross overs by turning off the cold water supply to the heater and I got no water out any of the single valves except the master I got a very marginal marginal trickle.

I have what I think is reasonable water pressure.

I have the water heater set to 110 degrees and am usually mixing somewhere around 50/50 to get the desired shower temp so I should not be getting into a low flow situation.

So...... where do I go from here? I'd like to be able to take more than a 4 minute shower someday.

Thanks in advance for your help.

 

[Ghostmaker]

Check your dip tube in the water heater. It might have dissolved. Its on the cold inlet and suppose to send the cold new water to the bottom of the tank.

 

[Help Help]

Thanks Ghost but I am using a tankless heater.

Next hypothesis?

 

[SHEPLMBR]

Thanks Ghost but I am using a tankless heater.

Next hypothesis?

Has it been serviced lately? Because there is no tank for the calcium flakes and all to build up they can clog the tankless. Their are a few descaling systems that can go in line before it to cut it down. But they have to be flushed pretty regularily

 

[srloren]

Has it been serviced lately? Because there is no tank for the calcium flakes and all to build up they can clog the tankless. Their are a few descaling systems that can go in line before it to cut it down. But they have to be flushed pretty regularily

Read your maintenance instructions that came with the tankless. Download them if you don't have a copy. Calcium needs to be dealth with by flushing with white vinegar on a regular basis or you diminish the life of the expensive tankless heater. Take a sample of your water to a Water Company and have it analysed .... sorry mis spelling.

 

[TheEplumber]

Is the Grohe valve thermostatic? Does the other valve act like this?

 

[Help Help]

The tankless was serviced 9 months ago and given a clean bill of health. This issue was present at that time and I had it serviced to eliminate that as a possible cause.

Thermostatic? If you mean pressure balancing, yes. The other valve is identical and not having any issues.

I'm starting to think it's the cartridge. But, I've replaced the cartridge twice. One time self identifying and getting one via the interweb and the other time sending a picture of the valve body to Grohe and having them identify the correct cartridge and send me one. The current cartridge has been in for about 10 months.

 

[Help Help]

Anyone?

 

[jimn]

Should not be the cartridge . My Moen cartridge before I redid the bathroom was 15 years old and functioned just fine. Unless you have a real issue with water quality , faucet cartridges shoul last years . 110 ten degree hot water? With my inlet temp that would guarantee a cold shower for 10 months of the year. I would still look at the water heater although I can give no advice. You couldn't give me a tankless water heater on a bet.

 

[ct18]

Not sure if it has been asked but it only happens at shower valve

 

[Help Help]

Steve, I think you could be on to it. It's only *THIS* shower valve and not in other showers on the same floor. It's the most used and while a quality fixture it's the typical low flow that California dictates. Usually there's no other water flowing in the house when we shower but for giggles I showered with hot water running on the nearby vanity and it seemed like the temp was good.

So, could I be up against the low flow limit of the tankless water heater? I'm going to clean the shower head and see about what could be restricting the flow.