Ask Me Help Desk - Hot water running cold in shower

We just had a new peerless tankless boiler put in our home. With the old boiler we had no problem with the hot water in the showers. However, when we replaced the shower controls I did have to make an adjustment on the pipes of the oil boiler. I turned a knob on one of the pipes that seemed to cut back the cold water and then the hot water was fine going to the showers. However, when they installed this new boiler, they repiped everything and that valve is no longer there. We have had 3 people come out and look at the boiler and only one was able to make an adjustment to the boiler to make it fire up faster so the water gets heated faster but we are still having a problem with the water getting cold. All 3 boiler guys said that the tankless boiler is too small and that we need to get a 40 gallon water tank added on to the boiler which will cost us even more money! The original contractor refuses to deal with the problem and says that the boiler is the right size. I am wondering if maybe it is another problem that we aren't aware of that would be less expensive. I forgot to mention that this is happening in upstairs and downstairs showers.

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Originally Posted by dianebrown

we just had a new peerless tankless boiler put in our home. With the old boiler we had no probelm with the hot water in the showers. However, when we replaced the shower controls i did have to make an adjustment on the pipes of the oil boiler. I turned a knob on one of the pipes that seemed to cut back the cold water and then the hot water was fine going to the showers. However, when they installed this new boiler, they repiped everything and that valve is no longer there. We have had 3 people come out and look at the boiler and only one was able to make an adjustment to the boiler to make it fire up faster so the water gets heated faster but we are still having a problem with teh water getting cold. All 3 boiler guys said that the tankless boiler is too small and that we need to get a 40 gallon water tank added on to the boiler which will cost us even more money! the original contractor refuses to deal with the problem and says that the boiler is the right size. I am wondering if maybe it is another problem that we arent aware of that would be less expensive. I forgot to mention that this is happening in upstairs and downstairs showers.

You swapped a oil fired hot water heater for a tankless of what size? How many elements and where did they install it? How far from your bathrooms?
What are the specs on the new tankless? How many GPM? How many in your family and how much of a draw do you make at one time? If three plumbers told you that the contractor undersized the installation then you have a case to take him to court and refund your money or to make the job right. Please keep me informed. Tom

No, we had a oil fired tankless about 40 years old and replaced it with a new one. I am not sure of the GPM - I think it said 129,000 there is a sticker on the boiler. I will have to write everything down when I get home. I know a boiler man who inspected it said it was a 3 sectional. The guy who installed it was suppose to be a "friend" and didn't give me any receipts, etc. All I have is a canceled check that was written out to his two workers. So taking him to court is out of the question I would think. He is also moving out of state. He is saying it is not too small and that it is a shower problem. I am giong to try adjusting the valves in the shower to see if that works. However, I am getting the same problem in my bathroom tub. If I slow the water down the water gets hotter. One shower is right down the hall from the boiler and the other one is right upstairs. I never had a problem with the old boiler after I adjusted the valve on the pipe on the boiler. I think it was some kind of a flow restricter valve. When they repiped the new boiler they took that valve off so now we have the problem. There is just me and my husband but we can't even take a shower at the same time and I noticed if the heat kicks in the water gets cold faster too. We have forced hot water cast iron baseboards.

Tom, did we let the red herring of a new, different hot water heater divert us from crud in the line?

Diane, look at the other posts in plumbing, where time after time Tom and I suggest opening up the shower valve and clean it out. All that repiping could have knocked crud loose in what was left and be caught in your shower valves. You may have even had trouble before, which why you had to cut the cold back. Post back with the brand and model of the shower valve, and Tom will give you good instructions on cleaning it.

One more thing. A year ago I was looking at gas tankless water heaters. I lost interest because if I read the specs right, they had a minimum flow for the heater to come on. I was afraid when I was over due to change the filter, not only would I have to shower in a trickle, but a cold trickle. Is yours electric?

Hi tom:

I got the model no, etc for the boiler. It's a peerless boiler #WBV-03-110-WPCTL Serial # 495948200409 IBR Burner Capacity is 1.1 Gross Output BTU/HR 129,000 BTU HR/Water 112,000

The valves are brand new - just installed under a year ago. We are getting hot water that is not the problem. It's just that it runs to lukewarm after 4 or 5 minutes until the boiler kicks in again. I talked with my plumber and he thinks that the boiler is too small. It is a 3 section and my house is a 3 bedroom 2 bath house with cast iron baseboards. The boiler is oil and electric. It is also happening when I turn the hot water on in the tub. The water runs cold after a while and then when I slow it down it gets hot again so I don't think it is the shower valves. Also, it is happening in both showers - one upstairs and one downstairs. I think that the boiler is too small and doesn't have time to catch up to the output of the water when taking showers or filling the tub.

The plumber says that we should have at least a 4 section or even 5 section boiler. We are giong to have to add on a hot water storage tank. He suggested a Amtrol tank which is added on as an additional zone to the boiler. They have the whole kit at home depot for $895 and it has a life time warranty. What do you think about this kind of hot water storage tank?

Take a look at http://sethglassman.com/Cartoon.jpg. This was recently discussed at https://www.askmehelpdesk.com/showthread.php?t=6195.

Ok, you have a hot water heater that uses a coil in the oil fired heating system to heat hot water. It replaced an similar, older system? If the older one worked, the newer one should too if it has a big enough coil. It sounds like adjusting the controls was a step in the right direction. Perhaps more adjustment is all that is needed.

I would try tweeking the current system before spending $1000 adding something else.

The valves on my shower are a temptrol and a simmyns(spelling). I still think that the new boiler is too small. My husband said that the old one was 116,000 and this one's BTU for hot water is 112,000 I guess. That to me would mean that it is too small. I noticed this morning while taking a shower that if I slowed the stream down that the water got hotter. So that means that the boiler is not big enough to keep up with the hot water flow when it is open full throttle right?? We are very frustrated and upset about all of this because we spent a lot of money to put this new boiler in and I think it has been adjusted as must as it can and we are giong to have to resort to buying a hot water storage tank to add onto it to get the hot water we need. Right now, we can't even take a shower at the same time which shouldn't be. Thanks anyway.