Tankless hot water delivery time/two different opinions

sandraca

I'm so glad I found this forum as we're at a loss concerning the problem with our tankless water heater delivery times. I've checked for this answer on the forum and I'm still confused. The unit is a Rinnali 2532 Continuum and is outside and directly behind the master bathroom. Yet it consistently takes full minutes running the tub at full force before it yields hot water. (Occasionally it will completely fail to deliver hot water at all and we'll wait a bit and try to get it to engage the next time though this seems to be a separate problem.) I can't get hot water at the bathroom sink unless someone's just showered. And trying to get hot water in the kitchen without the unit being previously engaged in a larger capacity is almost futile. Seriously, I could have the water running for 5 minutes and it would still be cold.

We've had two plumbers out for advice. The first said our pipes were too small. The exterior pipes appear to be at least an 1" if not larger. He talked about a pump to deliver the water faster but since it sits outside our bathroom that didn't seem a sensible solution. We're certainly not going to re-pipe. He also said that It appeared the unit installation was not up to code since it faces a 5' solid wall and the gas smell lingers. If that was done wrong, what else could have been done incorrectly?

The second plumber said the unit is very old and that it is too small for the house. He recommended that we replace it with a new and larger unit. His stated the pipe size was normal (but that we didn't have a TP line or some such thing though this seemed unrelated to the delivery time). I can't imagine the size of the unit would have anything to do with the hot water delivery time and he gave me an analogy that still didn't sound true. We are not having problems with multiple use of hot water which is what I've heard is the problem with a too small unit. The only issue is the delivery time of hot water. We live in S. California so our water never gets truly cold, cold.

I could get on board that the unit is too old and should be replaced but we need confidence this would solve the delivery time issue. So what could the problem be?

njtommy

Well we are going to need a little more information.
Is it city water?
What temp are you trying to achieve?
What temp is the cold water?

njtommy

Also how far is the run to kitchen?
Do you have problems when taking a bath only or when someone is showering

SWEI

Try shutting off the incoming cold water line to the heater. Unhook the hot water line coming out (and connect a short hose if necessary to route the water away.) Open the valve on the cold water line. Does hot water come out of the water heater?

4Johnpipe

How old is the unit? When was it last serviced? It may just have build up in the inlet screen. Has it ever coded off?

sandraca

I'll attempt to answer all questions. It's city water to start with and I'm guessing the unit is about 10 years old as the house was remodeled then (previous owner). No idea when it was last serviced and we've been here for 17 months. How this issue was not caught by the inspector when we purchased the house I don't know. The delivery time problem is found wherever there is interior running water. Assuming the pipes are in the crawlspace, the distance to the kitchen is around 30-40'. The upstairs bathrooms seem to wait approximately the same time for hot water as downstairs. As far as temperature goals, I'm guessing its set at a standard point since once the hot water starts going, that temperature is adequate. The cold water is a nice temperature but that's all the detail on have on that. If my husband showers and I follow him by 15 minutes or so, the line will initially still have hot water in it but not for long. Soon only cold water is running and I'm left in the cold shower for a couple of minutes before I get hot water again. This happened this morning. The unit has a hot and cold valve close to the ground and the plumber checked that by turning a valve on. The unit engaged (you can smell it) and I assume hot water came out. However, the hot water was already going throughout the downstairs since the dishwasher and washer were both on.
I just remembered we had one other plumber look at it very early on and I recollect him disliking the brand and that it was an old model.

Jamie Hall

A whole bunch of questions. But first -- that unit is still available. The particular one you have may be old, but they still make them, and generally they are very good.

They aren't really supposed to be installed outside. In fact, the manual (https://www.rinnai.us/documentation/downloads/V_Series_Indoor_25xx_U245-3250x0100_revised_A.pdf if you don't have a copy) quite specifically states that they should never be installed outside.

The manual also states -- correctly -- that you should not smell gas either when it is off or running. You mention that you can smell it when it is running. Not good, and suggests that it could really use a good cleaning and servicing.

Do you have the remote controller? That may show some error codes -- take a look at the manual I referenced above.

Keep in mind that this type of unit has a minimum flow to make it turn on. If your flow rate goes below that minimum, it won't make any hot water at all. When you are not getting hot water, does opening another hot water faucet somewhere help? It occurs to me that you may have a problem with too little flow, particularly if you have water saving faucets and shower heads.

Also -- keep in mind that it takes a while for the hot water from the unit to get through the pipe to your points of use! Nothing you can do about that!

sandraca

Jamie, You're getting warm with your last comment concerning the flow rate Granted, I know nothing about flow rate but I do know that if we turn the tub faucet full blast we get hot water faster and even better if that's going plus the shower. On the other hand, we've been in two other houses with this type of water heater and the flow rate seems the same.

Jamie Hall

The only reliable way to check flow rate is to actually time it. Take a bucket or pan with a known volume, and measure how long it takes to fill. Then compare that with the rated minimum flow of the unit.

Also keep in mind that there's a gallon of water in 30 feet of half inch pipe -- two gallons in that length of three quarter. That has to be emptied before any hot water will reach the fixture!

Water saving fixtures can be very deceptive.

sandraca

Jamie,
I forgot to thank you for the research you did on the unit and am alarmed that it is for indoor use only. Also, the reason you can smell gas is because there is a 5' solid wall about 3' away from the unit and the smell immediately dissipates. When we get a new one, which it looks like we will, it will be mounted higher for better ventilation. Again, this unit somehow bypassed inspection as it's clearly not to code.

Jack

The 2532 model was introduced in, mmm, 2001-2002 and was in the line for a few years. The model number changed, but the unit was essentially the same. The min flow on the 2532 is .6 gpm. At a 70* rise the unit will make 4.7 gpm all day long, if it is working correctly. There was an exterior model made and in S CA that is where most people put them. IF you have a touch pad control on the unit you can read the temp of the water exiting the unit, The flow rate in GPM and the fault code history of the unit. Without the touch pad, you are swinging in the dark.
At this point, the unit is 10-12 years old. You do not know the service history of the unit so that is a question. You need a service done by a certified Rinnai technician. The question for you is the balance of cost of service vs cost of a replacement unit. Now, your plumbing system is a problem, except for the master bath. !/2", 3/4" and 1" pipe have a cross sectional area of .19, .44 & .77 sq in. The number doesn't matter to you, but it relates to the volume of water in your system that needs to be displaced before you get water in the kitchen which is 50' away. That is a long aggravating wait.
Due to the lay-out of the system, you need a recirculating hot water system to get rid of that wait. There are after market systems, the Metlund Design being one of the best. Rinnai has a unit with the pump included as well as the recirc control if you decide to go that way. May I ask, where in S CA you are?
Just reading this over and pardon me, I'm a nitwit. Clean the filter on the cold water inlet. I bet that is it. Rinnai has a video on their web site showing how to do it. Otherwise, youtube is your friend. It is a simple procedure. Please report back.

sandraca

Jack, you're no wit nit! I try to find out how to do it on the Rinnai site. If it's that easy, I can do it without waiting for the weekend and or hubby. The unit does have a purifying system hooked up to it but I believe it's for hot water only.

sandraca

Jack, I checked out a video and am not comfortable with turning off the gas or the electric but my husband said he would try. Thanks for all your help and I'll let you know if we get in done and whether it works. Thanks again.
Sandra