Low hot water flow?

[SummerSteve]

After trailering our winterized C26 to Florida, we launched and all seemed well except that the hot water has maybe only 1/4 the flow of the cold water - I don't see anything that could be causing this - no filter or crimped hose. Plenty of pressure when the drain or top hose connection is opened at the heater. Low flow at both sinks, so not likely a problem with the faucets. Any suggestions appreciated!

 

[BB marine]

There is a check valve in the tank fitting. This valve is designed to not allow hot water to back out of the cold water inlet. The check valve is located ant the inlet. The check valve may be stuck restricting water flow. You must have cold water flow to the tank to get hot water flow out of the tank. If the flow of cold is restricted at the hot water tank all hot water lines will have low water pressure.

 

[Gin]

Brian, that’s interesting . . . I didn’t realize there is a check valve in the cold water inlet. Makes sense there would be one. On my system, the cold water comes in through the safety (pressure release) valve. Is the check valve part of the safety valve?

If so, I wonder if that has anything to do with the problem that some of us have with that valve “weeping” through the discharge opening at the bottom when the tank heats up. I’ve had that problem since my R31 was new. I’ve read several (maybe all) of the threads discussing that, and it seems to be inherent in the design. I have a replacement valve that I’ve never installed, because it looks like one of the biggest knuckle-buster jobs imaginable, and I keep having the sense I’ll have the same problem afterwards. But maybe not, if the check valve could be defective and might contribute to the amount of discharge I get warming up the tank. I’ve measured it a few times, and it usually is close to a quart’s worth when the water is stone cold. That seems like more than the “small quantity of water” that the Isotemp manual advises “can drain from the relief valve when the water is heated.” I wonder if a stuck or defective check valve would increase the discharge. On the other hand, my hot water pressure is fine.

If you or anyone else has thoughts on that, I’d welcome them.

Gini

 

[BB marine]

Gini, the cold water should not go into the tank Via the pressure relief valve. It actually can not. The pressure relief Valve is a one way valve that opens when the tank pressure exceeds the set pressure of the Relief Valve. Many times relief valves weep or leak after a pressure lift. During a pressure lift, small segments of debris can get stuck on the valve seat.This causes the valve to leak. There are times that a Relief valve once lifted doesn't alway seat properly. I rebuilt RV's when I worked at a petrochemical company. German high pressure and American standard ranging from pressures of 30 psi to 50000 psi. Once lifted were were required to remove and test them to confirm they still lived at set pressure and reseated properly. I believe you have a RV with crud on the seat or the seat is damaged.

The check valve is normally in the inlet port. A hot water heater will have two markings Cold inlet and Hot outlet. The check valve is installed in the cold side and looks like a pipe nipple.

 

[knotflying]

You might want to check your screens on the hot water side at the sinks as well. Perhaps all the on road jostling turned up some tank sediment and it clogged the screens.

 

[Gin]

Gini, the cold water should not go into the tank Via the pressure relief valve. It actually can not. The pressure relief Valve is a one way valve that opens when the tank pressure exceeds the set pressure of the Relief Valve. * * *

The check valve is normally in the inlet port. A hot water heater will have two markings Cold inlet and Hot outlet. The check valve is installed in the cold side and looks like a pipe nipple.

Brian, I've looked again at my setup and I see where I misunderstood it. You are right (which I didn't for a moment doubt). The cold water does not go through the PV. Both the cold water and the PV attach to a 4 way cross-fitting, using up two of the connections on the fitting. The cross-fitting is tapped into the tank at the "in" port, which uses a third connection. The fourth connection runs cold water up to the mixing valve on the hot water outlet. So, yes, I understand now that the cold water is not going through the PV. It bypasses it through the same cross-fitting. (That's the best I can do to explain it without using a photo).

All of which is consistent with the schematics for the connections in the Isotherm manual (which is here, for anyone who needs it: https://www.dropbox.com/sh/y792iogu...a?dl=0&preview=Indel+Webasto+Water+heater.pdf).

But it does seem odd to have the PV valve on the cold water side of the tank. And it makes me wonder if there is a check valve there. Seems like a check valve at the inlet would defeat the functioning of the pressure valve. I'm going to have to work more on my understanding of all of this!

As for the amount of water that discharges from the PV valve when the tank heats up, it does seem excessive. I have tried to flush out the valve, following the technique suggested (by you, Brian, as I recall) in an older thread. No improvement. So one of these days, perhaps I'll take that replacement project on. (My knuckles hurt just thinking about it).

Gini

 

[Cutwater28GG]

check the simple things first. do all taps show the same issue

remove the screens inside the taps and check for blockages.

sometimes I have had great success disconnecting the pipe from the tap unit as there is a screen sometime at that point before even getting to the tap.

 

[SummerSteve]

Thanks, Cutwater28GG - That was it - I had no idea there were screens between the nipple and sink connections! Full of crud only on the hot side at both sinks!

 

[knotflying]

You might want to check your screens on the hot water side at the sinks as well. Perhaps all the on road jostling turned up some tank sediment and it clogged the screens.

😀