I just installed a new 80 gal electric water heater and ever since I have low water pressure. Especially if I flush the toilet, then both hot and cold pressure will drop ( I saw a mixing valve for the toilet which may explain that). I have heard the plastic heat traps in the hot water heater's nipples may be the problem. Is that true?

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Originally Posted by JetEngineMech

I just installed a new 80 gal electric water heater and ever since I have low water pressure. Especially if I flush the toilet, then both hot and cold pressure will drop ( I saw a mixing valve for the toilet which may explain that). I have heard the plastic heat traps in the hot water heater's nipples may be the problem. Is that true?

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Whoa! Toilets don't have mixing valves, they only run on cold water. Do you mean bidet? A ball type nipple heat trap can set up flow restrictions and chattering at high flow rate. A inverted "U" formed out of flexible water connections, (see image) will not do this. Did this just start when you installed your heater or did installing the heater make a low pressure situation worse? Cheers, Tom

It appears these toilets do have mixing valves. I can see a hot and a cold line going into what is labeled "mixing valve" in the basement and from there to the toilet. Why? I don't know... These heat traps are down in the nipples of the hot water heater. I couldn't tell if they were ball or flapper, I didn't look at them long enough before connecting the plumbing. None of these problems started until after the water heater was installed.

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Originally Posted by JetEngineMech

It appears these toilets do have mixing valves. I can see a hot and a cold line going into what is labeled "mixing valve" in the basement and from there to the toilet. Why? I don't know...These heat traps are down in the nipples of the hot water heater. I couldn't tell if they were ball or flapper, I didn't look at them long enough before connecting the plumbing. None of these problems started until after the water heater was installed.

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There is only one reason to supply a toilet tank with hot water through a mixing valve. If there were a condensate,(sweat) problem on the tank hot water's metered into the tank to warm up the cold water. This would warm the water in the tank and prevent condensation from occurring. I have often offered this as a option, along with those fuzzy tank covers and cranking up the air to combat condensate on tanks but this is the first time I've ever heard of it being used.
To get back to your low pressure problem If were just the hot water I would tend to blaime the heat traps but since you experience a loss in both hot and cold I believe you disturbed mineral build up in your pipes and now it's clogging up the system cutting down on volume so you have a pressure loss.
This is not unusual for this to happen when replacing a faucet or a fixture.
The answer to this problem is to flush out the mains and branches first. Then each faucet that still runs slow will have to be opened up and cleaned and flushed. I realize this will be quite a task but the only other option is a repipe job and then you'll still have to deal with the faucets. Sorry I couldn't give you a better report but there isn't any other explanation. Regards. Tom

I'll give it a try and see how it goes. I'd rather do that than remove the traps and still have a problem. Thanks.

Yep, that did it. The cold line going into the heater had a lot of debris in it. Once I flushed it out the problem went away. Thanks again.

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Originally Posted by JetEngineMech

Yep, that did it. The cold line going into the heater had a lot of debris in it. Once I flushed it out the problem went away. Thanks again.

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Glad we could help. If we can ever be of service just call on us. Tom