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Hot bath water not so hot

Anyone know why my shower does not evenly mix hot and cold? In order to get a hot shower, the hot valve must be open half way and cold valve is closed or open slightly. Its oil fired heat and furnace is set to 130 but flow and mix is irregular. Will converting to a tankless hot water heater cure this problem?
James in CT

Re: Hot bath water not so hot

I had something similar to that happening at my house. What I found out was that my water regulator was just before my hot water tank and not on my whole system. So my hot water was set at 60 psi and the rest, or cold water, was city water presure which was 135 psi. So all you had to do was barely crack the cold water and it would override the hot. Moved regulator to control whole system and solved my problem. This was happening at all my fixtures though.

Re: Hot bath water not so hot

This could also be caused by a loose or worn washer or packing if it's an older 2- or 3-handle valve. If it's a "washerless" design, replacing the cartridge may solve the problem -- check the warranty, many cartridge faucets have a lifetime warranty.

Re: Hot bath water not so hot


Forget about a tankless system--it will cost over $1000 & the fix to your problem should cost next to nothing.

There are any one of 5 reasons why your shower is doing what it's doing---you'll have to do some detective work to find out which one it is.

First establish whether the hot water supply problem is restricted to the shower, or is present in ALL the faucets by opening the hot water on the vanity sink, then the kitchen sink, etc.

If the hot water water flow is low on ALL the hot water outlets, you have a problem with hot water flow from the HW heater.

If the low flow is only from the shower--concentrate on cleaning the shower head, the shower valve, checking the shower tempering valve (if one exists), the HW shower piping, etc.

From your post it sounds like you have a boiler with a domestic coil inside that makes the hot water (please verify how you hot water is heated)---sometimes these domestic coils cake up internally with calcium from hard water & have to be cleaned out (this would show up as low HW flow on ALL HW faucts).

There can be an adjustable tempering valve near the boiler that limits the amount of HW (especially to the shower)--try to find it & adjust.

Google "shower tempering valve" (without the quotation marks) to get photos of these valves & info on how they work.

The boiler also has a temp regulator to adjust the hW temp--this can be an adjustable gauge on the outside of the boiler, or more likely, an aquastat inside a small metal box that varies the HW temp (low limit) from 130 degrees to 180 degrees (high limit)---if you experience lukewarm water at all the HW faucets, move this "low limit" HW control to 150 degrees & see if there is an improvement---if you raise the "low limit", the "high limit" also has to be raised so it is always 20 degrees higher than the "low limit".

If you isolate the problem to just the shower, & the tempering valve is ok, check to see if there is crud buildup in the shower valve; also check in the shower valve for any worn washers---soaking the valve assembly in white vinegar or parts replacement is often done if the problem is isolated to the shower valve.

Check out the site below for troubleshooting ideas--at the site, click onto "solve a problem", then onto "tanklets", then onto "backflushing clogged piping".

Also Google "shower hot water loss" (without the quotation marks).


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