Greetings - Just replaced a failed 75 gal gas heater with 2 high efficiency 50 gal in tandem - Old heater had 1" inlet and outlets and there are 1" lines to master shower right up to shower head that did provide massive water volume
Now with the tandem set up and about 18" of 3/4" piping attached to the new 3/4" inlet and outlet piping connecting to the new 3/4" fittings the volume at shower head is dramatically decreased - can the inlet and outlets on the new heater be change to 1"? Thanks so much

"In tandem" does not tell us a whole lot. Are they in series or parallel, not that it should make a lot of difference in your volume?

My apology for tandem - meant "parallel"

Remove the new Shower head and check the filter screen for debris that may have been in the line when you replaced the old water heater. Turn the water on with the head not installed and let it run for a couple of seconds to clear any debris.

I will try that - any thoughts of the effect that the addition of two 18" long copper sections connecting to the new water heaters with 3/4" inlets and outlets vs the old 75 gal with 1" pipe all the way to heater with 1"inlets?
Thanks again

How many GPM is the showerhead ? I don't think you should be able to tell the difference between 3/4" or 1" pipe, unless there is another problem.

OP,

You have replaced one 1" pipe with two 3/4" pipes.

If actually parallel there should not be a problem.

If series there 'may' be an issue.

Best practice installation would be a 'reverse return' arrangement with 3/4" 'tails' connecting to the 1" which forces equal flow through both heaters due to the identical 'developed length' of piping through each.



ignore the pump, the piping is the point

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638



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In that case, you have some other problem, because the feeds to those two heaters is MUCH greater than any demand from your shower.

Should have absolutely no effect on it.

There is one other issue I can think of - but to recap - with old 75 Gal heater w 1" inputs and outputs on tanks with 1" piping both in and out directly to master bath shower with VERY high GPM capacity all was great - Changed to 2 50 gal with 3/4" inputs and outputs on tank with connected to about 18" of 3/4'" piping and then connected to the same 1" piping all the way to same master shower - House sevice is 1.5" Shower now not robust
One other change was that a back flow preventer was added on the 1" supply just before splitting the the 2 18" 3/4" tank supply. Shower head nozzles are clean.

Any more ideas greatly appreciated.

The 3/4" sections will force a velocity increase within them. The addition of 2 of them will carry more water than a single 1" line. That is not the source of your problem. What is the backflow preventer, and why was it installed?
Was an expansion tank installed after that backflow preventer?



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Thanks for the response - when I saw the back flow added just before the split from the previous single 1" sup;y to the new split 3/4" to each of the now 2 new heaters I asked what it was and why and plumber said "code" - My City building dept said it is not code and they are pretty tough
No there is not expansion tank and now plumber (without me asking) says he want to come back and add one - in my opinion the back flow should go and then no need for expansion tank- Do you thing the back flow could affect the lower volume of water IOm getting at shower head? Thanks again



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Possibly.....I'd have it removed.

ditto

==============================================

"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

Hello Op
Would you please elaborate on reason for "Reverse Return" for the cold water display ? Dose that insure equal volume cold water supply to both tanks and if so - how does that equate to equal out put to the new 3/4" hot pies?
I am still getting reduced water volume to master shower - I an having the cold inline check valve removed as it is not code as the installer had told me and am thinking that may be part of the issue.